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: Time Limit Exceeded)

using System;
 
    public class Program
    {
        public static void Main(string[] args)
        {
string Q=Console.ReadLine();
            bool Z=true;
            while ((Q!="")&&Z)
            {
                if (Q.Substring(Q.Length-5)=="dream") Q=Q.Substring(0,Q.Length-5);
                else if (Q.Substring(Q.Length-5)=="erase") Q=Q.Substring(0,Q.Length-5);
                else if (Q.Substring(Q.Length-6)=="eraser") Q=Q.Substring(0,Q.Length-6);
                else if (Q.Substring(Q.Length-7)=="dreamer") Q=Q.Substring(0,Q.Length-7);
                else Z=false;
            }
            if (Z==false) Console.WriteLine("NO"); else Console.WriteLine("YES");
        }
    }