// correct

#include <cassert>
#include <cmath>
#include <iostream>

long long solve(const long long x, const long long n) {
    long long l = 0, r = 2'000'000'000;
    assert(r * (r + 1) / 2 > 1'000'000'000'000'000'000);
    while (r - l > 1) {
        long long m = (l + r) / 2;
        long long sum = m * (m + 1) / 2;
        if (x > 0) {
            (x - sum <= 0 ? r : l) = m;
        } else {
            (x + sum > 0 ? r : l) = m;
        }
    }
    const long long k = std::min(n, l);
    long long d = k * (k + 1) / 2;
    if (n > k) {
        if ((n - k) % 2) {
            d += r + (n - k) / 2;
        } else {
            d -= (n - k) / 2;
        }
    }
    return x > 0 ? x - d : x + d;
}

int main() {
    long long x, n;
    std::cin >> x >> n;
    std::cout << solve(x, n) << std::endl;
}