using System;
using System.Linq;

namespace Problem1048
{
    class Program
    {
        static void Main(string[] args)
        {
            var LRMK = GetLongArray();
            long L = LRMK[0];
            long R = LRMK[1];
            long M = LRMK[2];
            long K = LRMK[3];

            long quoL = L * K % M == 0 ? L * K / M : L * K / M + 1;
            
            if (L * K <= quoL * M && quoL * M <= R * K)
            {
                Console.WriteLine("Yes");
            }
            else
            {
                Console.WriteLine("No");
            }
        }
        public static long[] GetLongArray() => Console.ReadLine().Split().Select(long.Parse).ToArray();

    }
}