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
fscanf(STDIN, "%s", $s);
$array = array('dream', 'dreamer', 'erase', 'eraser');

$s = strrev($s);
$array = array_map('strrev', $array);

while($s[4]){
    if(in_array(substr($s, 0, 5), $array)){
        $s = substr($s, 5);
    }elseif(in_array(substr($s, 0, 6), $array)){
        $s = substr($s, 6);
    }elseif(in_array(substr($s, 0, 7), $array)){
        $s = substr($s, 7);
    }else{
        break;
    }
}
if(strlen($s) === 0){
    print 'YES';
}else{
    print 'NO';
}