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
$words = ["dream", "dreamer", "erase", "eraser"];

fscanf(STDIN, "%s", $S);

while($S) {
    $flg = false;
    
    foreach ($words as $word) {
        $len = strlen($word);
        $exam = substr($S, -$len);
        if ($exam === $word) {
            $S = substr($S, 0, strlen($S) - $len);
            $flg = true;
            break;
        }
    }
    
    if ($flg === false) break;
}

echo $S === "" ? "YES\n" : "NO\n";