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 Scala (2.11.7) (judge verdict: Accepted)

import io.StdIn.readLine


object Main {

  def main(args: Array[String]): Unit = {
    var s = readLine()
    var state = 0

    while (state == 0) {
      if      (s.endsWith("dream"))   s = s.slice(0, s.length - 5)
      else if (s.endsWith("dreamer")) s = s.slice(0, s.length - 7)
      else if (s.endsWith("erase"))   s = s.slice(0, s.length - 5)
      else if (s.endsWith("eraser"))  s = s.slice(0, s.length - 6)
      else if (s.isEmpty) state = 1
      else              state = 2
    }
    state match {
      case 1 => println("YES")
      case 2 => println("NO")
    }
  }

}