class Student {
public:
    Student(int x, int y) {
        a = x;
        b = y;
    }
    Student( ) {

    }
    ~Student() {

    }
    int a;
    int b;

    int flag;

    void set_flag (int f) {
        flag = f;
    }

    bool operator==(const Student &student1) {
        if (flag == 1) return (a == student1.a);
        else return (b == student1.b); // if flag == 2 and ...
    }
};