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: Accepted)

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

  $s = strrev($s);

  while($s != ""){
    if(substr($s, 0, 5) == 'maerd'){
      $s = substr($s, 5);
      continue;
    }
    if(substr($s, 0, 7) == 'remaerd'){
      $s = substr($s, 7);
      continue;
    }
    if(substr($s, 0, 5) == 'esare'){
      $s = substr($s, 5);
      continue;
    }
    if(substr($s, 0, 6) == 'resare'){
      $s = substr($s, 6);
      continue;
    }
    echo "NO";
    exit;
  }
  echo "YES";