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 Common Lisp (SBCL 1.1.14) (judge verdict: Time Limit Exceeded)

(defun solve (s)
  (let ((solved nil))
    (labels
      ((f (s)
               (if (loop for word in '("dream" "dreamer" "erase" "eraser") do
                      (let ((mismatch (mismatch s word)))
                        (cond ((not mismatch) (setf solved t))
                               ((= mismatch (length word)) 
                                (f (subseq s (length word)))))))
                  t nil)))
      (f s))
      (format t "~A~%" (if solved "YES" "NO"))))

(defun main ()
  (solve (read-line)))

(main)