import java.io.*;
import java.util.*;
import java.math.BigInteger;
public class Solution {

    public static void main(String[] args) {
        Scanner input = new Scanner(System.in);
        BigInteger n = input.nextBigInteger();
        BigInteger m = input.nextBigInteger();
        BigInteger ans = n.multiply(m);
        BigInteger one = new BigInteger("1");
        ans = ans.subtract(one);
        
        System.out.println(""+ans);
        /* Enter your code here. Read input from STDIN. Print output to STDOUT. Your class should be named Solution. */
    }
}