#include<iostream>
#include<cstdio>
#include<algorithm>
#include<cmath>
#include<vector>
using namespace std;
#define ll long long

const int maxn = 1e2 + 10;
const int INF = 0x3f3f3f3f;

int main()
{
    int a,b;
    cin >> a >> b;
    if(a > 0)
        b = -1 * b;
    else
        b *= 2;
    if(b * b % 2 == 1)
    {
        if(b < 0 && a > 0)
            a = -1 * a;
        if(b > 0 && a < 0)
            a = -1 * a;
    }
    else
    {
        if(b < 0 && a < 0)
            a = -1 * a;
        if(b > 0 && a > 0)
            a = -1 * a;
    }
    printf("%d\n",a - b);
}