# include <bits/stdc++.h>
using namespace std;
typedef long long ll; 
//# define int long long
# define lc u << 1
# define rc u << 1 | 1
# define fi first
# define se second

int a, b;
signed main ()
{
//	freopen ("missing.in", "r", stdin); freopen ("missing.out", "w", stdout);  
	scanf ("%d%d", &a, &b);
	if (a < b) printf ("%d\n", b - 2);
	else if (a > b) printf ("%d\n", 2000000000 - b - 1);
	else printf ("0\n");
	return 0;
}