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

public class Solution {

    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        String start = in.next();
        String end = in.next();
        BigInteger obj=new BigInteger(start);
        BigInteger obj1=new BigInteger(end);
        BigInteger one = new BigInteger("1");
        obj = obj.subtract(one);
        obj = obj.multiply(obj1);
        obj1 = obj1.subtract(one);
        obj1 = obj.add(obj1);
    
        System.out.println(obj1);
    }
}