#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
#define in(T,V) T V;cin>>V;

int main(){
    in(ll,A);
    in(ll,B);

    ll res = 0;
    if(A < B){
        res = B-2;
    } else {
        res = 2000000000-B-1;
    }
    cout << res << endl;
}