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: Accepted)

check :: String -> Bool
check "resare" = True
check "esare" = True
check "remaerd" = True
check "maerd" = True
check (c1:c2:c3:c4:c5:c6:c7:cs)
    | head5 == "resar" = if c6 == 'e'
                         then check (c7:cs)
                         else False
    | head5 == "esare" = check $ c6:c7:cs
    | head5 == "remae" = if (c6:c7:[] == "rd")
                         then (check cs)
                         else False
    | head5 == "maerd" = check $ c6:c7:cs
    | otherwise = False
    where head5 = c1:c2:c3:c4:c5:[]
check _ = False
 
main :: IO ()
main = do
    sentence <- getLine :: IO String
    putStr $ if (check $ reverse sentence) then "YES" else "NO"