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) {
        /* Enter your code here. Read input from STDIN. Print output to STDOUT. Your class should be named Solution. */
        Scanner sc = new Scanner(System.in);
        long n = sc.nextLong();
        long m = sc.nextLong();
        
        if(n==1 && m==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);
        }
            
        
    }
}