Problem:
Score : 300 points

Problem Statement

You are given a string S consisting of lowercase English letters.
Another string T is initially empty.
Determine whether it is possible to obtain S = T by performing the following operation an arbitrary number of times:

Append one of the following at the end of T: dream, dreamer, erase and eraser.

Constraints

1≦|S|≦10^5

S consists of lowercase English letters.

Input

The input is given from Standard Input in the following format:

S

Output

If it is possible to obtain S = T, print YES. Otherwise, print NO.

Sample Input 1

erasedream

Sample Output 1

YES

Append erase and dream at the end of T in this order, to obtain S = T.

Sample Input 2

dreameraser

Sample Output 2

YES

Append dream and eraser at the end of T in this order, to obtain S = T.

Sample Input 3

dreamerer

Sample Output 3

NO

Solution in C# (Mono 4.6.2.0) (judge verdict: Accepted)

using System;

public class Program
{
	public static void Main()
	{
		string[] strs = { "dream", "dreamer", "erase", "eraser" };
		var S = Console.ReadLine();
		int i = S.Length;
		while (i > 0)
		{
			bool flg = false;
			foreach (var str in strs)
			{
				if (i >= str.Length)
				{
					if (S.Substring(i - str.Length, str.Length) == str)
					{
						i -= str.Length;
						flg = true;
					}
				}
			}
			if (!flg)
			{
				Console.WriteLine("NO");
				return;
			}
		}
		Console.WriteLine("YES");
	}
}