#include <iostream>
#include <string>
using namespace std;

class IntMod
{
private:

    int num;
    int mod;

public:

    IntMod(int num = 0, int mod = 1) : num(num % mod), mod(mod) {}
    IntMod operator+(const IntMod& other);
    void get();
};

void IntMod::get()
{
    cout << this->num << endl;
}

IntMod IntMod::operator+(const IntMod& other)
{
    if (this->mod == other.mod)
        return IntMod((this->num + other.num) % this->mod, this->mod);
}

int main()
{
    IntMod a, b(13,21), c(10,21),d(5,21);
    a = (b + c);
    a.get();
    return 0;
}