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 (5.6.30) (judge verdict: Time Limit Exceeded)

<?php
$inS = fgets(STDIN);
$inS = str_replace(array("\r\n","\r","\n"), "", $inS);

while(true) {
  $tem2 = substr($inS, -2, 2);
  $tem5 = substr($inS, -5, 5);
  $tem6 = substr($inS, -6, 6);
  $tem7 = substr($inS, -7, 7);
  if ($tem2 == 'er') {
    if ($tem7 == 'dreamer') {
      $inS = preg_replace("/dreamer\$/", '', $inS);
      continue;
    } elseif ($tem6 == 'eraser' ) {
      $inS = preg_replace("/eraser\$/", '', $inS);
      continue;
    } else {
      break;
    }
  } elseif ($tem5 == 'dream') {
      $inS = preg_replace("/dream\$/", '', $inS);
      continue;
  } elseif ($tem5 == 'erase') {
      $inS = preg_replace("/erase\$/", '', $inS);
      continue;
  }
  break;
}

echo strlen($inS) === 0 ? 'YES' : 'NO';

?>