#include <bits/stdc++.h>
#define F first
#define S second
#define all(x) begin(x), end(x)
#define pb push_back
#define FOR(i, a, b) for (int i = (a); i <= (b); i++)
#ifdef LOCAL
#define HEHE freopen("in.txt", "r", stdin);
#define debug(HEHE...) cerr << #HEHE << " = ", dout(HEHE)
void dout() { std::cerr << '\n'; }
template <typename T, typename ...U>
void dout(T t, U ...u) { std::cerr << t << ' '; dout(u...); }
#else
#define HEHE ios_base::sync_with_stdio(0), cin.tie(0);
#define debug(...) 7122
#endif
using namespace std;

#define chmax(a, b) (a) = (a) > (b) ? (a) : (b)
#define chmin(a, b) (a) = (a) < (b) ? (a) : (b)

#define int long long

signed main() {
    HEHE
    // 2
    // 2 - 1 - 2 +3-4+5-6
    // 
    int x, n;
    cin >> x >> n;
    if (x <= 0 and n <= 2e9 and x + (n + 1) * n / 2 <= 0) {
        cout << x + (n + 1) * n / 2 << '\n';
        return 0;
    }
    if (x > 0 and n <= 2e9 and x - (n + 1) * n / 2 > 0) {
        cout << x - (n + 1) * n / 2 << '\n';
        return 0;
    }
    int t = sqrt((abs(x) + 1)*2) + 10;
    if (x <= 0) {
        while (x + t * (t + 1) / 2 > 0) t--;
        x += t * (t + 1) / 2;
        // x + (t+1) - (t+2)...
        if ((t+1+n) % 2) {
            cout << x - (n - t) / 2 << '\n';
        }
        else {
            cout << x - (n - 1 - t) / 2 + n << '\n';
        }
    }
    else {
        while (x <= t * (t + 1) / 2) t--;
        x -= t * (t + 1) / 2;
        // cout << x << '\n';
        if ((t+1+n) % 2) {
            cout << x + (n - t) / 2 << '\n';
        }
        else {
            cout << x + (n - 1 - t) / 2 - n << '\n';
        }
    }
    // t + 1 ~n
}