#include <bits/stdc++.h>
using namespace std;

using ll = long long;
using llu = long long unsigned;

// メイン関数
int main() {
    int a, b;
    cin >> a >> b;
    int ret = a%b;
    while (ret < 0) {
        ret+=b;
    }
    cout << ret << endl; return 0;
}