#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
const int INF=0x3f3f3f3f;
const ll LLINF=0x3f3f3f3f3f3f3f3fLL;
const int MAX=2e5+10;
const int mod=998244353;
int main()
{
	ll x,n,now,i,target;
	scanf("%lld%lld",&x,&n);
	if(x<=0) target=-x;
	else target=x;
	now=sqrt(2*target);
	while((1+now)*now/2>=target) now--;
	while((1+now)*now/2<=target) now++;
	now=min(n,now-1);
	if(x>=0) x-=(1+now)*now/2;
	else x+=(1+now)*now/2;
	if(x<=0)
	{
		now++;
		x+=now;
	}
	x+=(n-now)/2;
	for(i=now+(n-now)/2*2+1;i<=n;i++)
	{
		if(x<=0) x+=i;
		else x-=i;
	}
	printf("%lld\n",x);
	return 0;
}