M_N_3.cpp

#include <iostream>
using namespace std;

class Q;
class P {
    private:
      int x;
    public:
      P()
        {
            x=10;
        }
      friend int add(P, Q);
};

class Q {
    private:
       int y;
    public:
       Q()
        {
            y=2;
        }
       friend int add(P , Q);
};

int add(P objectA, Q objectB)
{
   return (objectA.x + objectB.y);
}

int main()
{
    P objectA;
    Q objectB;
    cout<<"Addition: "<< add(objectA, objectB);
    return 0;
}

==========================output=============================
 Addition: 12