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

int main()
{
long long A;
long long B;
const long long iLim = 2000000000;

	cin >> A;
	cin >> B;

	if( A > B )
		cout << iLim - B - 1 << endl;
	else
		cout << B - 2 << endl;

	return 0;
}