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)

object Main extends App {
  var s = scala.io.StdIn.readLine()
  val tSeq = Seq("dreamer", "eraser", "dream", "erase")

  def judgeInclude(sInput: String): Boolean = {
    var sTemp = sInput
    while(true) {
      tSeq.find(t => sTemp.endsWith(t)) match {
        case Some(t) =>
          if(t == sTemp) {
            return true
          } else {
            sTemp = sTemp.dropRight(t.length)
          }
        case _ =>
          return false
      }
    }
    return false
  }
  
  if (judgeInclude(s)) {
    println("YES")
  } else {
    println("NO")
  }
}