package m.shin;
import java.util.Scanner;
public class Con339 {

	public static void main(String[] args) {
		Scanner s = new Scanner(System.in);
		int a = s.nextInt() , b = s.nextInt();
		s.close();

		int d;
		if(a < b){
			d = b - 2;
		}else{
			d = 1999999999 - b;
		}
		System.out.println(d);

	}

}