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: Wrong Answer)

<?php

$stdin = fopen('php://stdin', 'r');

$buf = fgets($stdin);
$buf = trim($buf);

while (true) {
    if ($buf == '') {
        echo 'YES';
        exit();
    }

    if (preg_match('/^dreamer/', $buf)) {
        $buf = substr($buf, 7, 10000);
        continue;
    }
    if (preg_match('/^dream/', $buf)) {
        $buf = substr($buf, 5, 10000);
        continue;
    }
    if (preg_match('/^eraser/', $buf)) {
        $buf = substr($buf, 6, 10000);
        continue;
    }
    if (preg_match('/^erase/', $buf)) {
        $buf = substr($buf, 5, 10000);
        continue;
    }

    echo 'NO';
    exit();
}

echo 'NO';