#include<iostream>
#include<string>

#define MAX (2000000000)

using namespace std;

int main(){
    int a,b;
    cin >> a >> b;
    int result;
    if(a<b){
        result = b-2;
    }
    else {
        result = MAX-b-1;
    }
    cout << result << endl;

    return 0;
}