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