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 (5.26.1) (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"