ABC087A - Buying Sweets

問題：A - Buying Sweets

#include <iostream>
using namespace std;

int main(void) {
    int x, a, b;

    cin.tie(0);
    ios::sync_with_stdio(false);
    cin >> x;
    cin >> a;
    cin >> b;
    cout << (x - a) % b << "\n";
    return 0;
}