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

namespace YukiCoder
{
    class Program
    {
        static void Main(string[] args)
        {
            var  va  = Console.ReadLine().Split().Select(long.Parse).ToArray();
            long sum = Console.ReadLine().Split().Select(long.Parse).Sum();
            if (va[0] * va[1] == sum) Console.WriteLine("YES");
            else                      Console.WriteLine("NO");
            Console.ReadLine();
        }
    }
}