#!/bin/python3

import sys


n,m = input().strip().split(' ')
n,m = [int(n),int(m)]

if n==1 and m==1:
    print(0)
    sys.exit(0)
    
if m > n:
    t = n
    n = m
    m = t

if n == 1:
    n = 2

print((n-1)*m + (m-1))