# include <bits/stdc++.h>
using namespace std;
typedef long long ll;

ll a, b;

int main()
{
	scanf("%lld%lld", &a, &b);
	if (a < b)
	{
		printf("%lld\n", b - 2);
	}
	else if (a > b)
	{
		printf("%lld\n", 2000000000 - b - 1);
	}
	else puts("0");
	return 0;
}