Switch statement Practice

#include <iostream.h>
#include <conio.h>
int main ()
{
    clrscr ();
    int student;
    float a=0,b=0;
    float p=0;
    float f=0;
    int n=0;
    char g=' ';
    cout <<"Enter The Number Of Students : ";
    cin >> student;
    cout <<endl;
    while (n<student)
    {
    cout <<"Enter A Grade : ";
    cin >> g;
    switch (g)
    {
        case 'a':
        case 'b':
        case 'c':
        case 'd':    ++p;
        break;
        case 'f':    ++f;
    }
    n++;
    }
    a=((p/student)*100);
    b=((f/student)*100);
    cout << p <<" Students Are Passed  "<< a <<" % "<<endl;
    cout << f <<" Students Are Failed " << b <<" % "<<endl;
    getch();
    return 0;
}