// (⁠◕⁠ᴗ⁠◕⁠✿⁠)

// #pragma GCC target("avx2")
#pragma GCC optimize("O3")
#pragma GCC optimize("unroll-loops")
#include <bits/stdc++.h>
#define rep(i, n) for (ll i = 0; i < (n); i++)
#define srep(i, s, n) for (ll i = s; i < (n); i++)
#define len(x) ((int)(x).size())
#define all(x) (x).begin(), (x).end()
using namespace std;
template<typename T> using vc = vector<T>;
template<typename T> using vv = vc<vc<T>>;
template<typename T> using vvv = vv<vc<T>>;
using vi = vc<int>;using vvi = vv<int>; using vvvi = vv<vi>;
using ll = long long;using vl = vc<ll>;using vvl = vv<ll>; using vvvl = vv<vl>;
using ld = long double; using vld = vc<ld>; using vvld = vc<vld>; using vvvld = vc<vvld>;
using uint = unsigned int;
using ull = unsigned long long;
const ld pi = acos(-1.0);
const int inf = 0x3f3f3f3f;
const ll INF = 0x3f3f3f3f3f3f3f3f;
// const ll mod = 1000000007;
const ll mod = 998244353;
inline bool inside(ll y, ll x, ll H, ll W) {return 0 <= (y) and (y) < (H) and 0 <= (x) and (x) < (W); }

#define debug(var)  do{std::cout << #var << " : \n";view(var);}while(0)
template<typename T> void view(T e){cout << e << endl;}
template<typename T> void view(const vc<T>& v){for(const auto& e : v){ cout << e << " "; } cout << endl;}
template<typename T> void view(const vv<T>& vv){ for(const auto& v : vv){ view(v); } }

int main(){
    ll x, n; cin >> x >> n;
    auto f = [&](ll p){
        if (INF / p < (p + 1) / 2) return INF;
        return p * (p + 1) / 2;
    };
    ll top = n + 1, bottom = 0;
    while (top - bottom > 1){
        ll mid = (top + bottom) / 2;
        if (f(mid) <= abs(x)) bottom = mid;
        else top = mid;
    }
    if (bottom == n){
        if (x >= 0) x -= bottom * (bottom + 1) / 2;
        else x += bottom * (bottom + 1) / 2;
        cout << x << endl;
        return 0;
    }
    if (x >= 0){
        x -= bottom * (bottom + 1) / 2;
    }else{
        bottom++;
        x += bottom * (bottom + 1) / 2;
    }
    if ((n - bottom) % 2){
        x -= (bottom + 1);
        x -= (n - bottom) / 2;
        cout << x << endl;
    }else{
        x += (n - bottom) / 2;
        cout << x << endl;
    }
}