import java.util.*;

public class Main {
	static Scanner sc = new Scanner(System.in);
	public static void main(String[] args) {
		int left = sc.nextInt();
		int center = sc.nextInt();
		int right = 0;
		if (left < center) {
			right = center - 2;
		}
		else if (left > center) {
			right = 2000000000 - left;
		}
		System.out.println(right);
	}
}