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

int main() {
	int x, n;
	cin >> x >> n;
	
	for (int i = 0; i < n; i++) {
		if (x <= 0) {
			x += i;
		}
		else {
			x -= i;
		}
	}
	
	cout << x << endl;
}