#include <iostream>
using namespace std;
int main() {
long long a, b;
cin >> a >> b;
if (b > 0) {
if (a / b >= 0) {
cout << a - (a / b + 1) * b;
} else {
cout << a - a / b * b;
}
} else {
if (a / b <= 0) {
cout << a - (a / b + 1) * b;
} else {
cout << a - a / b * b;
}
}
return 0;
}
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