#include <iostream>
#include <vector>
#include <cstdio>
#include <sstream>
#include <map>
#include <string>
#include <algorithm>
#include <queue>
#include <cmath>
#include <functional>
#include <set>
#include <ctime>
#include <random>
using namespace std;
template<class T> istream& operator >> (istream& is, vector<T>& vec){for(T& val: vec) is >> val; return is;}
template<class T> istream& operator , (istream& is, T& val){ return is >> val;}
template<class T> ostream& operator << (ostream& os, vector<T>& vec){for(int i=0; i<vec.size(); i++) os << vec[i] << (i==vec.size()-1?"\n":" ");return os;}
template<class T> ostream& operator , (ostream& os, T& val){ return os << " " << val;}
template<class T> ostream& operator >> (ostream& os, T& val){ return os << " " << val;}
bool is_kadomatsu_sequence(vector<int> x){
    if(x.size() != 3) return false;
    if(x[0] < x[1] && x[1] > x[2] && x[2] != x[0]) return true;
    if(x[0] > x[1] && x[1] < x[2] && x[2] != x[0]) return true;
    return false;
}
int main(){
	int a,b;
	cin >> a,b;

	long long ans = 0;
	if(a<b){
		if(a==1 && b==2){
			ans = 0;
		}else{
			ans = b-2;
		}
	}else{
		if(b==2000000000-1){
			ans = 0;
		}else{
			ans = 2000000000 - b - 1;
		}
	}
	cout << ans << endl;

	return 0;
}