#include <iostream>
using namespace std;

class A {
    int data;
public:
    A(int data = 0) : data(2*(data/2)) { }

    const A operator-() const {
        return A(-data);
    }

    const A operator-(A& a) const {
        return A(data - a.data);
    }

    A& operator--() {
        ----data;
        return *this;
    }

    const A operator--(int) {
        A x(data);
        ----data;
        return x;
    }

    friend ostream& operator<<(ostream&,A);
};

ostream& operator<<(ostream& strum, A d) {
    return strum << d.data;
}

int main() {
    A data(7);

    cout << "a.   data    = " <<   data   << endl;
    cout << "b.   data--  = " <<   data-- << endl;
    cout << "c.   data    = " <<   data   << endl;
    cout << "d. --data    = " << --data   << endl;
    cout << "e.   data    = " <<   data   << endl;
    cout << "f.  -data    = " <<  -data   << endl;
    cout << "g.   data    = " <<   data   << endl;
}