#include <bits/stdc++.h>
using namespace std;
#define rep(i, n) for (int i = 0; i < (int)(n); i++)
int main(){
    cin.tie(0)->sync_with_stdio(0);
    cout.tie(0);
    long long x,n;
    cin>>x>>n;
    long long cnt=1;
    long long x2;
    if(x>0){
        while(x>0){
            x-=cnt;
            if(cnt==n){
                cout<<x<<endl;
                return 0;
            }
            cnt++;
        }
        x2=x+cnt;
        if((n-cnt)%2==0){
            cout<<x2+(n-cnt)/2<<endl;
        }
        else{
            cout<<x-(n-cnt+1)/2<<endl;
        }
    }
    else if(x<0){
        while(x<=0){
            x+=cnt;
            if(cnt==n){
                cout<<x<<endl;
                return 0;
            }
            cnt++;
        }
        x2=x-cnt;
        if((n-cnt)%2==0){
            cout<<x2-(n-cnt)/2<<endl;
        }
        else{
            cout<<x+(n-cnt+1)/2<<endl;
        }
    }
    else{
        x=0;
        x2=1;
        if((n-cnt)%2==0){
            cout<<x2+(n-cnt)/2<<endl;
        }
        else{
            cout<<x-(n-cnt+1)/2<<endl;
        }
    }
}