#include <stdio.h>
#include <math.h>

int main() {
	int a,b,c,d;
	scanf("%d %d",&a,&b);
	if(a>0){
		b = -1*b;
	}else
	b = b*2;
	c = abs(b);
	 if(b!=0&&a/abs(a) == b/c)
				if(c%2!=0)
				a =1*a;
				else
				 a = -1*a;
	   else
	    if(c%2!=0)	
		a = -1*a;
		else
		a = 1*a;
				 
	
	d=a-b;
	printf("%d\n",d);
	return 0;
	
}