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 m1=new Scanner(System.in);
        long n=m1.nextLong();
        long m=m1.nextLong();
        long temp1=0;
        long temp2=0;
        if(n-1>0){
            temp1=(n-1)*m;
        }else{
            temp1=-1;
        }
        if(m-1>0){
            temp2=(m-1)*n;
        }else{
            temp2=-1;
        }
        if(temp1<temp2){
            if(temp1==-1){
                System.out.println(temp2);
            }
            else{
                System.out.println(temp1);
            }
        }else{
            if(temp2==-1){
                System.out.println(temp1);
               
            }else{
                System.out.println(temp2);
            }
        }
    }
}