#include<bits/stdc++.h>
#include<atcoder/all>
#define rep(i,n) for(int i=0;i<n;i++)
using namespace std;
using namespace atcoder;
typedef long long ll;
typedef vector<int> vi;
typedef vector<long long> vl;
typedef vector<vector<int>> vvi;
typedef vector<vector<long long>> vvl;
typedef long double ld;
typedef pair<int, int> P;

template <int m> ostream& operator<<(ostream& os, const static_modint<m>& a) {os << a.val(); return os;}
template <int m> ostream& operator<<(ostream& os, const dynamic_modint<m>& a) {os << a.val(); return os;}
template <int m> istream& operator>>(istream& is, static_modint<m>& a) {long long x; is >> x; a = x; return is;}
template <int m> istream& operator>>(istream& is, dynamic_modint<m>& a) {long long x; is >> x; a = x; return is;}
template<typename T> istream& operator>>(istream& is, vector<T>& v){int n = v.size(); assert(n > 0); rep(i, n) is >> v[i]; return is;}
template<typename U, typename T> ostream& operator<<(ostream& os, const pair<U, T>& p){os << p.first << ' ' << p.second; return os;}
template<typename T> ostream& operator<<(ostream& os, const vector<T>& v){int n = v.size(); rep(i, n) os << v[i] << (i == n - 1 ? "\n" : " "); return os;}
template<typename T> ostream& operator<<(ostream& os, const vector<vector<T>>& v){int n = v.size(); rep(i, n) os << v[i] << (i == n - 1 ? "\n" : ""); return os;}
template<typename T> ostream& operator<<(ostream& os, const set<T>& se){for(T x : se) os << x << " "; os << "\n"; return os;}
template<typename T> ostream& operator<<(ostream& os, const unordered_set<T>& se){for(T x : se) os << x << " "; os << "\n"; return os;}
template<typename S, auto op, auto e> ostream& operator<<(ostream& os, const atcoder::segtree<S, op, e>& seg){int n = seg.max_right(0, [](S){return true;}); rep(i, n) os << seg.get(i) << (i == n - 1 ? "\n" : " "); return os;}
template<typename S, auto op, auto e, typename F, auto mapping, auto composition, auto id> ostream& operator<<(ostream& os, const atcoder::lazy_segtree<S, op, e, F, mapping, composition, id>& seg){int n = seg.max_right(0, [](S){return true;}); rep(i, n) os << seg.get(i) << (i == n - 1 ? "\n" : " "); return os;}

template<typename T> void chmin(T& a, T b){a = min(a, b);}
template<typename T> void chmax(T& a, T b){a = max(a, b);}

int main(){
	long long x, n;
	cin >> x >> n;
	
	long long ng = -1, ok = 2002002002;
	while(ok - ng > 1){
		long long mid = (ok + ng) / 2;
		long long diff = mid * (mid + 1) / 2;
		if(x > 0){
			if(x - diff <= 0) ok = mid;
			else ng = mid;
		}else{
			if(x + diff > 0) ok = mid;
			else ng = mid;
		}
	}
	if(n <= ok){
		long long diff = n * (n + 1) / 2;
		if(x > 0){
			cout << x - diff << "\n";
		}else{
			cout << x + diff << "\n";
		}
		return 0;
	}
	long long y = 0;
	{
		long long diff = ok * (ok + 1) / 2;
		if(x > 0){
			y = x - diff;
		}else{
			y = x + diff;
		}
		assert(abs(y) <= ok);
	}
	if((n - ok) % 2){
		ok ++;
		if(y <= 0) y += ok;
		else y -= ok;
	}
	{
		long long ans = y;
		if(y <= 0) ans -= (n - ok) / 2;
		else ans += (n - ok) / 2;
		cout << ans << "\n";
	}
	return 0;
}