#include "pch.h"
#include <iostream>
#include <clocale>
#include <string>
#include <clocale>
using namespace std;

class dog {
    friend class person;
private:
    int health = 100;
};
class person {
public:
    void damage(dog d) {
        d.health -= 20;
    }
};
int main(int argc, const char * argv[]) {
    person vasya;
    dog bobik;
    cout << vasya.damage(bobik);
    return 0;
}