#include <stdio.h>

int main (void){
	long a,b;
	long max=2000000000;
	long ans=0;
	scanf("%d %d",&a,&b);
	if(a<b){
		if(b-a==1){
			ans = a-1;
		}else{
			ans=a-1+a-b;
		}
	}else{
		ans= max-a;
	}
	printf("%d\n",ans );
	return 0;
}