import java.util.*;

public class Main {
    static final int MAX = 2000000000;
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int a = sc.nextInt();
        int b = sc.nextInt();
        int ans;
        if (a > b) {
            ans = MAX - b - 1;
        } else {
            ans = b - 2;
        }
        System.out.println(ans);
    }
}