#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;
}