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 Haskell (GHC 7.10.3) (judge verdict: Time Limit Exceeded)

{-# OPTIONS_GHC -O2 -funbox-strict-fields #-}

main :: IO ()
main = putStrLn =<< solve <$> getLine


solve :: String -> String
solve s
    | solve' s  = "YES"
    | otherwise = "NO"

solve' :: String -> Bool
solve' "" = True
solve' s = any (match s) ts where
    ts = ["dreameraser", "dreamerase", "dreamer",
          "dream", "eraser", "erase"]

match :: String -> String -> Bool
match s t
    | take n s == t = solve' $ drop n s
    | otherwise     = False where
          n = length t