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 Perl6 (rakudo-star 2016.01) (judge verdict: Time Limit Exceeded)

use v6;
my $s = get().chomp;
while ($s ne "") {
	if ($s ~~ m/dreamer$$|dream$$|eraser$$|erase$$/) {
		$s ~~ s/dreamer$$|dream$$|eraser$$|erase$$//;
	} else {
		last;
	}
}
if ($s eq "") {
	say "YES";
} else {
	say "NO";
}
exit;