#include <iostream>

using namespace std;

int main() {
    int number_1, number_2, sum;
    cin >> number_1 >> number_2 >> sum;
    int current_sum = number_1 + number_2;
    if (number_1 + number_2 != sum) {
         cout << "Error. The sum of "s << number_1 << " and "s << number_2 << " is "s << current_sum << endl;
    }
return 0;
}