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

public class Test
{
	public static void Main()
	{
		var f = Console.ReadLine()
				.Split(' ')
				.Select(x => int.Parse(x))
				.ToList();
		var s = Console.ReadLine()
			.Split(' ')
			.Select(x => int.Parse(x))
			.ToList();
		var h = ((s[0] - 1) / f[1]) % 2 == 0 ? (s[0] - 1) % f[1] : f[1] - ((s[0] - 1) % f[1]) -1;
		var t = ((s[1] - 1) / f[1]) % 2 == 0 ? (s[1] - 1) % f[1] : f[1] - ((s[1] - 1) % f[1]) -1;
		var ans  = "";
		if(h == t) ans = "YES";
		else ans = "NO";
		Console.WriteLine(ans);
	}
}