#include <iostream>
#include <string>

using namespace std;

class A{
    double b;

    public:
    A(double arg) : b(arg){};
    virtual double virt_method(double a, double b)=0;


};


class B: public A{
    double virt_method(double a, double b){
        return (a+b);
    }
    B(double a):A(0){};




};

int main()
{

}