#include <stdio.h>
#include <bits/stdc++.h>
#include <atcoder/all>
using namespace atcoder;
using mint = modint998244353;
using namespace std;
#define rep(i,n) for (int i = 0; i < (n); ++i)
#define Inf32 1000000000
#define Inf64 1000000000000000001LL

int main(){
	
	long long x,n;
	cin>>x>>n;
	long long nn = n;
	long long ok = 0;
	long long ng = 2000000005;
	long long over;
	if(x > 0)over = x;
	else over = -x+1;
	while(ng-ok>1LL){
		long long mid= (ok+ng)/2;
		if(mid * (mid+1) / 2 <over)ok = mid;
		else ng = mid;
	
}

	if(ok >= n){
		if(x <= 0)x += n*(n+1)/2;
		else x -= n*(n+1)/2;
	}
	else{
		if(x<=0)x += ok*(ok+1)/2;
		else x -= ok*(ok+1)/2;
		n -= ok;
		if(x<=0)x -= n/2;
		else x += n/2;
		n %= 2;
		if(n){
			if(x<=0)x += nn;
			else x-=nn;
		}
	}
	cout<<x<<endl;
	return 0;
}