#include <cstdio>
#include <iostream>
#include<string>
#include<algorithm>
using namespace std;
int main()
{
	int a,b;
	cin>>a>>b;
	if(b==0)
	{
		cout<<-a<<endl;
	}
	else
	{
	if(a>0)
		b=-b;
	else
		b*=2;
	if(abs(b)%2==1)
	{
		if(b/abs(b)==1)
		{
			if(a<0)
				a*=-1;
		}
		if(b/abs(b)==-1)
		{
			if(a>0)
				a*=-1;
		}
	}
	else
	{
		if(b/abs(b)==1)
		{
			if(a>0)
				a*=-1;
		}
		if(b/abs(b)==-1)
		{
			if(a<0)
				a*=-1;
		}
	}
	cout<<a-b<<endl;
	}
}