#include <iostream>

#define LL long long
#define MAX 2000000000

using namespace std;

int countPattern(LL left, LL center)
{
	LL right_count = 0;
	if(left < center) {
		
		right_count += center - left - 2;
		
	} else {
		
		right_count += MAX - center - 1;
		
	}
	
	return right_count;
}

int main()
{
	LL left = 0;
	LL center = 0;
	
	cin >> left >> center;
	
	cout << countPattern(left, center) << endl;
	
	return 0;
}