import java.io.*;
import java.util.*;

public class Solution {

    public static void main(String[] args) {
        /* Enter your code here. Read input from STDIN. Print output to STDOUT. Your class should be named Solution. */
       Scanner in = new Scanner(System.in);
        long n = in.nextLong();
        long m = in.nextLong();
        
        if (m == 1 && n==1)
            System.out.println(0);
        else if (m == 1)
            System.out.println(n-1);
        else if(n==1)
            System.out.println(m-1);
        else
            System.out.println(n*m-1);
        in.close();
    }
}