#include <iostream>

using namespace std;

int main() {
    int x, y, z ;
	cin >> x >> y >> z;
	int r = x + y;
	if ((x + y) != z){
		cout << "Error. The sum of "s << x << " and "s << y << " is "s << r << endl;
	}

}
// теперь и мой прошел