Using Function in a Class

#include <iostream>
using namespace std;
class a{
      public:
      int i,j;
      int cros(int, int)
      {
           return i*j;
      }
};
int main()
{
    int vol;
    int p=7;
    int q=8;
    a aa;
    aa.i=7;
    aa.j=5;
    //vol=a.i*a.j;
    cout<<aa.i<<aa.j<<endl;
    cout<<aa.cros(p,q)<<endl;
    system("pause");
    return 0;
}

This is the output:

75
35