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
$S = trim(fgets(STDIN));
$T = '';

while (1) {
    if (strpos($S, 'eraser')!==false) {
        $S = str_replace('eraser', '', $S);
    }elseif (strpos($S, 'erase')!==false) {
        $S = str_replace('erase', '', $S);
    }elseif (strpos($S, 'dreamer')!==false) {
        $S = str_replace('dreamer', '', $S);
    }elseif (strpos($S, 'dream')!==false) {
        $S = str_replace('dream', '', $S);
    }
    else {
        break;
    }
}

echo $S==$T ? 'YES': 'NO';