#include<stdio.h>
#include<math.h>
int main()
{
	int a,b;
	scanf("%d %d",&a,&b);
	if(a>0){
		b=-1*b;
	} else {
		b=2*b;
	}
	if(abs(b)%2==1){
		a=abs(a)*(b/abs(b));
	} else if(abs(b)%2==0&&b!=0){
		a=-1*abs(a)*(b/abs(b));
	} else if(b==0){
		a=abs(a)*(-1);
	}
	printf("%d",a-b);
}