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 sc = new Scanner(System.in);
        
        long n = sc.nextLong();
        long m = sc.nextLong();
        
        //if(n * m % 2 == 1)
            System.out.println(n * m - 1);
        //else
            //System.out.println(n * m - 2);
    }
}