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 PHP7 (7.0.15) (judge verdict: Accepted)

<?php

//$_input = explode(
//    "\n",
//    'dreamerasererasedream
//'
//);

function getNext() {
    return trim(
        isset($GLOBALS['_input'])
            ? array_shift($GLOBALS['_input'])
            : fgets(STDIN)
    );
}

function buildable($s, $arr) {
    while (true) {
        foreach ($arr as $value) {
            if (strpos($s, $value) === 0) {
                $s = substr($s, strlen($value));

                if ($s === '') {
                    return true;
                }

                continue 2;
            }
        }

        return false;
    }
}

printf("%s\n", buildable(strrev(getNext()), array_map(function ($s) { return strrev($s); }, ['dream', 'dreamer', 'erase', 'eraser'])) ? 'YES' : 'NO');