import java.util.*;
import java.math.*;
import java.text.*;

public class Main {
    private static Scanner sc = new Scanner(System.in);
    public static void main(String[] args) throws Exception {
        int a = sc.nextInt();
        int b = sc.nextInt();
        
        int ret;
        if (a < b) {
            ret = b - 2;
        } else {
            ret = 2000000000 - b - 1;
        }
        
        System.out.println(ret);
    }
}