using System;
using System.Linq;

class Program
{
    static void Main()
    {
        long[] i = Console.ReadLine().Split().Select(long.Parse).ToArray();
        long h = i[0];
        long w = i[1];
        long n = i[2];
        long k = i[3];

        long a = h * w;
        a %= n;
        if (a == 0) a = n;

        if (k == a) Console.WriteLine("YES");
        else Console.WriteLine("NO");

    }
}