#include <iostream>
using namespace std; 
class sample
{
    int a, b; 
    public:
    void setvalue()
    {
        a=25;
        b=40;
    }
    friend float mean (sample s);
};
float mean (sample s)
{
    return (s.a+s.b)/2.0;
}
int main() {
    sample x; 
    x. setvalue();
    cout <<"mean value ="<<mean(x);
    return 0;
}