#include <stdio.h>

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