Please check my code....??

[itguy310]

#include <iostream.h>
int main()
{
    int grade;
    cout<<"Please enter obtained marks: ";
    cin>>grade;
    if (grade >= 90)
    cout<<"Your Grade is: 'A'\n";
    else if (grade >=80)
    cout<<"Your Grade is: 'B'\n";
    else if (grade >=70)
    cout<<"Your Grade is: 'C'\n";
    else if (grade >= 0)
    cout<<"Please increase your numbers for attractive grade. Thanks!\n";
    system ("pause");
}

This grading code to show the grade according to abtaining marks. but it ends up when it complete first output like when i entered marks one time it shows its relevant grade and then it terminates but i want it to keep continue to get other marks.? how to do that ?