Need a little help :)

So recently i made this code for my homework:

Code:

---

#include <iostream>
using namespace std;
int main()

{
  int date;
  int month;
  char ans;
  cout<<"Enter your birth month and date to determine your zodiac sign\n\n"<<endl;

    while (!((ans=='n') || (ans=='N')))
    {
    cout<<"Enter your birth month:";
    cin>>month;
    cout<<"Enter your birth date:";
    cin>>date;
 
   
    if (( month == 1 && date >= 20 && date <= 31 ) || ( month == 2 && date <=18 ))
    {
        cout<<"Your zodiac sign is AQUARIUS\n\n";
        cout<<"Aquarius is an old constellation. As the Water Carrier or Water Bearer,\nhe is carved in stones";
        cout<<"of the Babylonian Empire and probably is still older than that period.\n";
       
    }
    else if (( month == 2 && date >= 19 && date <= 28) || ( month == 3 && date <= 20))
    {
        cout<<"Your zodiac sign is PISCES\n\n";
        cout<<"Pisces was named after Aphrodite and Eros.The story of Pisces originated from\n";
        cout<<"the destructive monster, Typhon.\n";
    }
    else if (( month == 3 && date >= 21 && date <= 31) || ( month == 4 && date <= 19))
    {
        cout<<"Your zodiac sign is ARIES\n\n";
        cout<<"Aries is a zodiacal constellation representing the ram of the Golden\n";
        cout<<"Fleece sought by Jason and the Argonauts.\n";
       
    }
    else if (( month == 4 && date >= 20 && date <= 30 )  || ( month == 5 && date <= 20))
    {
        cout<<" Your zodiac sign is TAURUS\n";
    }
    else if (( month == 5 && date >= 21 && date <= 31 )  || ( month == 6 && date <= 20 ))
    {
        cout<<" Your zodiac sign is GEMINI\n";
    }
    else if (( month == 6 && date >= 21 && date <= 30 ) || ( month == 7 && date <= 22 ))
    {
        cout<<" Your zodiac sign is CANCER\n";
    }
    else if (( month == 7 && date <= 23 && date <= 31) || ( month == 8 && date <= 22))
    {
        cout<<" Your zodiac sign is LEO\n";
    }
    else if (( month == 8 && date >= 23 && date <= 31) || ( month == 9 && date <= 22 ))
    {
        cout<<" Your zodiac sign is VIRGO\n";
    }
    else if (( month == 9 && date >= 23 && date <= 30) || ( month == 10 && date <= 22))
    {
        cout<<" Your zodiac sign is LIBRA\n";
    }
    else if (( month == 10 && date >= 23 && date <= 31 ) || ( month == 11 && date <= 21))
    {
        cout<<" Your zodiac sign is SCORPIO\n";
    }
    else if (( month == 11 && date >= 22 && date <= 30 ) || ( month == 12 && date <= 21))
    {
        cout<<" Your zodiac sign is SAGUITTARIUS\n";
    }
    else if (( month == 12 && date >= 22 && date <= 31 ) || ( month == 1 && date <= 19 ))
    {
        cout<<" Your zodiac sign is CAPRICORN\n";
       
    }
    else
    {
        cout<<" INVALID INPUT\n";
    }
    cout<<"do you want to continue? y/n"<<endl;
    cin>>ans;
    }
    if ( ans == 'n')
    {
        cout<<"Thank you for your precious time! :D\n\n";
    }

    system("pause");

}

---

but now i have another problem..the problem is i need to have a invalid input when the program asks "do you want to continue? Y/N"..for ex:

Do you want to continue? Y/N :
z (this is the input)
Sorry, i can only determine yes or no.

something like that..

I am posting this reply for the OP or anyone else who might have the same question.
I am sorry if there are any errors. Do note that this code is not optimized, but it should be helpful.

Please, feel free to use the code for any purpose.

Code:

---

#include <iostream>
#include <string>
#include <sstream>

using namespace std;

// Declare your functions up front. Define them later.
// You don't have to write out the full names here, as it is obvious
//  what these functions are for.

void coutAries ( void );
void coutTaurus ( void );
void coutGemini ( void );
void coutCancer ( void );
void coutLeo ( void );
void coutVirgo ( void );
void coutLibra ( void );
void coutScorpio ( void );
void coutSagittarius ( void );
void coutCapricorn ( void );
void coutAquarius ( void );
void coutPisces ( void );

// Using enum can help prevent logical errors.
// Just remember, the first value in any array is located in index 0.
// Any easy way to solve this problem is to simply label the first
//  element to the number you desire. The elements following the
//  labeled one will continue from there.
/*
        const enum
        {
                JANUARY = 1,
                FEBRUARY,
                MARCH,
                APRIL,
                MAY,
                JUNE,
                JULY,
                AUGUST,
                SEPTERMBER,
                OCTOBER,
                NOVEMBER,
                DECEMBER
        };
*/

// You can also use shorthand for months. They, too, are obvious.
const enum
{
        JAN = 1,
        FEB,
        MAR,
        APR,
        MAY,
        JUN,
        JUL,
        AUG,
        SEP,
        OCT,
        NOV,
        DEC
};

// This function returns the upper bound of the date range according
//  to month.

// The easiest way to return a months maximum date, is to use an array.
// Remember, our number for January is 1, so we need to either subtract
//  1 from 'month' or use a placehold in our array.
const int monthMaxDate[13] =
{ 0, 31, 29, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31 };

int dateMax ( int month )
{
        return monthMaxDate[month];
}
// I think I have an extensive piece of code that checks for leap years
//  as well. But, I'll leave that fun up to you. :)

// Here is a function that I have sitting around. It can be used
//  to convert a C++ string into a number. It returns the result
//  as an integer.

int stringToInt ( const string & String )
{
        stringstream Stream ( String );
        int Result;
        return ( Stream >> Result ) ? Result : 0;
}

int main ()
{
        // When naming variables, you should be as specific as possible.
        // Also, try to use the smallest type possible. In this case,
        //  a char would be the best choice, because it is a single byte.
        char userDate, userMonth;
        string userInput;

        // For while checking, I would suggest something a bit different.
        // There is nothing wrong with checking the input for a value type.
        // However, it is easier to manage a variable with the specific task
        //  of iterating the loop.

        // You can use any data type here, but a 1 byte type saves space.
        bool exitLoop = false;

        // Now we can simply check for one value here. This method saves
        //  nothing. However, it is far clearer and easier to read.
        while ( exitLoop == false )
        {
                // Initialize your variables to zero.
                userDate = 0;
                userMonth = 0;
                userInput = "";

                // This output should ideally go here, in case you want to restart
                //  the main loop so that the user can run it again.

                // I like letting my users exit when entering a blank.
                // But I forgot, it takes some other code to do, so nevermind that for now.
                cout <<
                        "Enter your birth month and date to determine your Zodiac sign.\n"
                        << endl;

                // Now, I have a very helpful library that makes input validation
                //  10 times easier. However, I am not ready to have my code
                //  picked apart by other programmers here.

                // I'll show you a simple way to validate your user input.
                // Idealy, you would want to use a C++ string for this task.
                // Strings are easy to use, and prevent many errors that
                //  you might encounter with a C string.

                // First, we drop everything into our string type userInput variable.
                // Then, using some functions, we can check the input to see if it
                //  complies with what we are asking for.

                // The point of this program is to tell the user which zodiac sign
                //  he or she is. It would be rather pointless to continue the
                //  program if the user enters invalid data at any step in the
                //  input process. Therefore, we should confront the user if
                //  he or she gives an invalid input, then re-prompt.

                // For this program, I believe this is the easiest and fastest
                //  way to check for proper input.
                while ( userMonth == 0 )
                {
                        cout << "Enter your birth month: ";
                        cin >> userInput;

                        // This is the easiest way to exit the loop and then program.

                        // Now we shall convert the input into a number. Our function
                        //  will do all the dirty work for us. If the input was not a number,
                        //  the result will be 0.
                        userMonth = stringToInt ( userInput );

                        // Finally, we check to make sure the data is in the proper range.
                        if ( userMonth < 1 || userMonth > 12 )
                        {
                                userMonth = 0;
                                cout << " INVALID INPUT\n";
                        }
                }

                while ( userDate == 0 )
                {
                        cout << "Enter your birth date: ";
                        cin >> userInput;

                        userDate = stringToInt ( userInput );

                        // Now, checking for the range of the month is easy. There are only
                        //  12 months. However, the the date range varies month to month.
                        // To fix this, we will use a function! It depending on the month
                        //  the user entered, it will give us the upper bound of the date
                        //  range.
                        if ( userDate < 1 || userDate > dateMax ( userMonth ) )
                        {
                                userDate = 0;
                                cout << " INVALID INPUT\n";
                        }
                }

                // Here, we can use a series of conditional statements. Though,
                //  it would be far easier and less time consuming to use a different
                //  method. However, I assume this is assignment specific.

                // Instead, let me fix up some redundancy, make the list easier to read.

                // For zodiac signs, I would start with January, and check for
                //  the low order dates first. Notice that there is no reason to
                //  do full bounds checking here. Your input validation should
                //  do all the bounds checking for you, prior to this part.

                if ( userMonth == JAN )
                {
                        if ( userDate <= 19 )
                        {
                                coutCapricorn ();
                        }
                        else // if ( userDate >= 20 )
                        {
                                coutAquarius ();
                        }
                }

                if ( userMonth == FEB )
                {
                        if ( userDate <= 18 )
                        {
                                coutAquarius ();
                        }
                        else // if ( userDate >= 19 )
                        {
                                coutPisces ();
                        }
                }

                if ( userMonth == MAR )
                {
                        if ( userDate <= 20 )
                        {
                                coutPisces ();
                        }
                        else // if ( userDate >= 21 )
                        {
                                coutAries ();
                        }
                }

                if ( userMonth == APR )
                {
                        if ( userDate <= 19 )
                        {
                                coutAries ();
                        }
                        else // if ( userDate >= 20 )
                        {
                                coutTaurus ();
                        }
                }

                if ( userMonth == MAY )
                {
                        if ( userDate <= 20 )
                        {
                                coutTaurus ();
                        }
                        else // if ( userDate >= 21 )
                        {
                                coutGemini ();
                        }
                }

                if ( userMonth == JUN )
                {
                        if ( userDate <= 20 )
                        {
                                coutGemini ();
                        }
                        else // if ( userDate >= 21 )
                        {
                                coutCancer ();
                        }
                }

                if ( userMonth == JUL )
                {
                        if ( userDate <= 22 )
                        {
                                coutCancer ();
                        }
                        else // if ( userDate >= 23 )
                        {
                                coutLeo ();
                        }
                }

                if ( userMonth == AUG )
                {
                        if ( userDate <= 22 )
                        {
                                coutLeo ();
                        }
                        else // if ( userDate >= 23 )
                        {
                                coutVirgo ();
                        }
                }

                if ( userMonth == SEP )
                {
                        if ( userDate <= 22 )
                        {
                                coutVirgo ();
                        }
                        else // if ( userDate >= 23 )
                        {
                                coutLibra ();
                        }
                }

                if ( userMonth == OCT )
                {
                        if ( userDate <= 22 )
                        {
                                coutLibra ();
                        }
                        else // if ( userDate >= 23 )
                        {
                                coutScorpio ();
                        }
                }

                if ( userMonth == NOV )
                {
                        if ( userDate <= 21 )
                        {
                                coutScorpio ();
                        }
                        else // if ( userDate >= 22 )
                        {
                                coutSagittarius ();
                        }
                }

                if ( userMonth == DEC )
                {
                        if ( userDate <= 21 )
                        {
                                coutSagittarius ();
                        }
                        else // if ( userDate >= 22 )
                        {
                                coutCapricorn ();
                        }
                }

                // Now we should ask if the user wants to rerun the program.
                cout << "\n\nWould you like to re-run the program? (Y/N) ";
                while ( exitLoop == false )
                {
                        cin >> userInput;

                        if ( userInput == "Y" || userInput == "y")
                        {
                                cout << "\n\n";
                                break;
                        }
                        else if ( userInput == "N" || userInput == "n")
                        {
                                exitLoop = true;
                                break; // This break isn't necessary.
                        }
                        else
                        {
                                cout << "Please enter Y to re-run the program or N to exit. (Y/N) ";
                        }
                }
        }

        // There is no reason to check this. You should always thank your users,
        //  before the program exits.
        //if ( userInput == "n" )
        //{
        cout << "\n\nThank you for your precious time! :D\n\n";
        //}

        // I suggest that you do not use System Pause. It is cpu expensive,
        //  and other programmers simply love to make fun of people who use it.
        // Now. The fact that you are trying to pause the program makes the
        //  cpu expense rather a pointless argument. The real reason they don't
        //  like it is because it isn't very portable. And it's windows. Haha

        // If you want to use System Pause, go ahead. Though, you should
        //  understand that console applications are 'supposed' to be run under
        //  some form of console. This defeats the purpose of the System Pause
        //  at the end of a program. It simply does no good as a console will
        //  stay open even after the program finishes. But, most people don't
        //  really know what a console is and how to use it, so they just
        //  double click an exe file and hope it works.

        //system ("pause");
}

void coutAries ( void )
{
        // Instead of breaking up your output into separate statements like this,
        //  you should look up a help document on strings in C/C++.
        cout << "Your zodiac sign is ARIES\n\n"
                "Aries is a zodiacal constellation representing the ram of the Golden\n"
                "Fleece sought by Jason and the Argonauts.\n";
}

void coutTaurus ( void )
{
        cout << "Your zodiac sign is TAURUS\n";
}

void coutGemini ( void )
{
        cout << "Your zodiac sign is GEMINI\n";
}

void coutCancer ( void )
{
        cout << "Your zodiac sign is CANCER\n";
}

void coutLeo ( void )
{
        cout << "Your zodiac sign is LEO\n";
}

void coutVirgo ( void )
{
        cout << "Your zodiac sign is VIRGO\n";
}

void coutLibra ( void )
{
        cout << "Your zodiac sign is LIBRA\n";
}

void coutScorpio ( void )
{
        cout << "Your zodiac sign is SCORPIO\n";
}

void coutSagittarius ( void )
{
        cout << "Your zodiac sign is SAGUITTARIUS\n";
}

void coutCapricorn ( void )
{
        cout << "Your zodiac sign is CAPRICORN\n";
}

void coutAquarius ( void )
{
        cout << "Your zodiac sign is AQUARIUS\n\n"
                "Aquarius is an old constellation. As the Water Carrier or Water Bearer,\n"
                " he is carved in stones of the Babylonian Empire and probably is still older than that period.\n";
}

void coutPisces ( void )
{
        cout << "Your zodiac sign is PISCES\n\n"
                "Pisces was named after Aphrodite and Eros. The story of Pisces originated from\n"
                " the destructive monster, Typhon.\n";
}

---

Fixed a couple mistakes, haha.