Hello guys,

Thanks for your help and suggestions. I managed to solve this task without converting to string. Here is my code if someone is interested:

Code:
#include <iostream>
#include <cstdlib>

using namespace std;

void separate(int number)
{
    // If the number is below 1000 - print it because it holds exactly or below 3 digits
    if (number < 1000)
    {
        cout << number;
    }
    else
    {
        int temp = number % 1000; // Variable which holds the remainder of the calculation (the last 3 digits of the integer)
        number = number / 1000; // Remove the last 3 digits and pass the remaining of the integer again to the function
        separate(number);
        cout << "," << temp;
    }
}

int main()
{
    int input;
    cout << "Enter your number :" << endl;
    cin >> input;
    separate(input);
    cout << endl;

    system("PAUSE");
    return 0;
}