#include <iostream> using namespace std; class B { int x; public: B(int i = 10) { x = i; } int get_x() { return x; } }; class D : public B { public: D(int i) : B(i) { } D operator+(const D& a) { return x + a.x; } }; int main() { D ob1(7), ob2(-12); cout << (ob1 + ob2).get_x(); return 0; }