#ifdef NACHIA
#define _GLIBCXX_DEBUG
#else
#define NDEBUG
#endif
#include <iostream>
#include <string>
#include <vector>
#include <algorithm>
using i64 = long long;
using u64 = unsigned long long;
#define rep(i,n) for(i64 i=0; i<i64(n); i++)
const i64 INF = 1001001001001001001;
template<typename A> void chmin(A& l, const A& r){ if(r < l) l = r; }
template<typename A> void chmax(A& l, const A& r){ if(l < r) l = r; }
using namespace std;

void testcase(){
    i64 X, N; cin >> X >> N;
    i64 ok = 0, ng = 2001001001;
    if(ng > N+1) ng = N+1;
    bool sw = X < 0;
    if(sw) X = -X;
    while(ok + 1 < ng){
        i64 x = (ok + ng) / 2;
        i64 y = x * (x+1) / 2;
        if(y <= X) ok = x; else ng = x;
    }
    X -= ok * (ok + 1) / 2;
    if(sw) X = -X;
    if(ok == N){
        cout << X << "\n"; return;
    }
    if(X > 0){ X -= ok+1; ok++; }
    i64 t = (N - ok) / 2;
    ok += t * 2;
    X -= t;
    if(ok < N) X += ++ok;
    cout << X << "\n";
}

int main(){
    ios::sync_with_stdio(false); cin.tie(nullptr);
    testcase();
    return 0;
}