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

int main() {
    LL a,b;
    cin>>a>>b;
    if(a>b){
        cout<<(2000000000ll-b-1)<<endl;;
    }
    else{
        cout<<(b-2)<<endl;
    }
    return 0;
}