#include <iostream>
using namespace std;

int main() {
	long long a, b;
	cin >> a >> b;
	
	long long r = a - a / b * b;
	
	if (a >= 0 && b >= 0) {
		cout << ;
	} else {
		cout << min(r, abs(r - (a / b + 1)* b))
	}
	
	
	return 0;
}