/*  This Code is Submitted by wywcgs for Problem 2267 on 2006-06-03 at 17:20:14 */ 
#include <cstdio>

int main()
{
	int n, m;
	
	while(scanf("%d %d", &n, &m) != EOF && !(n == 0 && m == 0))
		printf("%d\n", 3*n-m);
	
	return 0;
}