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 Perl (v5.18.2) (judge verdict: Accepted)

@T=map {scalar reverse $_} ("dream","dreamer","erase","eraser");
$s=<>;
chomp($s);
$s=reverse($s);
$l=length($s);
for($c=0;$c<$l;){
	$k=-1;
	for($i=0;$i<4;$i++){
		if(substr($s,$c,length($T[$i])) eq $T[$i]){
			$k=length($T[$i]);
			last;
		}
	}
	if($k<0){
		print'NO';
		exit
	}
	$c+=$k;
}
print'YES'