using System;
using System.Collections;
using System.Collections.Generic;
using System.Linq;



 class Program
{


	public static void Main()
	{
		
		long[] triangle = Console.ReadLine().Split(' ').Select(long.Parse).ToArray();
            long triX = triangle[1];
            long triN = triangle[0];
            Console.Write(triX*(((triN+triX)/2)+1)+(triX/2)*(((triN+triX)/2)+1));
	}
}	
	
	
	