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: Accepted)

<?php
$s = strrev(trim(fgets(STDIN)));
$divide = ['dream', 'dreamer', 'erase', 'eraser'];
foreach ($divide as $k => $v) {
    $divide[$k] = strrev($v);
}
$can = true;
for ($i = 0; $i < strlen($s);) {
    $can2 = false;
    foreach ($divide as $v) {
        if (strpos($s, $v, $i) === $i) {
            $can2 = true;
            $i += strlen($v);
        }
    }
    if (! $can2) {
        $can = false;
        break;
    }
}
echo $can ? 'YES' : 'NO';
?>