#include <iostream>
using namespace std;

int main() {
    int a, b, c;
    cin >> a >> b >> c;

    int s = a + b + c;
    for(int i = 0; i < 10; i++) {
        if((s + i) % 3 == 0) {
            cout << i << endl;
            break;
        }
    }
    return 0;
}