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