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. */
        long n,m,c;
        Scanner in=new Scanner(System.in);
        n=in.nextLong();
        m=in.nextLong();
        if(n==1 && m==1)
            System.out.println(0);
        else if(n==1)
            System.out.println(m-1);
        else if(m==1)
            System.out.println(n-1);
            else
        {
            c=n*m-1;
        System.out.println(c);
        }
    }
}