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 PHP (7.4.4) (judge verdict: Memory Limit Exceeded)

<?php
  list($s) = explode(" ", trim(fgets(STDIN)));

  $s = strrev($s);

  if(f($s)){
    echo "YES";
  }else{
    echo "NO";
  }

  function f($s){
    if($s == ""){
      return true;
    }
    if(substr($s, 0, 5) == 'maerd'){
      if(f(substr($s, 5))){
        return true;
      }
    }
    if(substr($s, 0, 7) == 'remaerd'){
      if(f(substr($s, 7))){
        return true;
      }
    }
    if(substr($s, 0, 5) == 'esare'){
      if(f(substr($s, 5))){
        return true;
      }
    }
    if(substr($s, 0, 6) == 'resare'){
      if(f(substr($s, 6))){
        return true;
      }
    }
    return false;
  }