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: Wrong Answer)

{-# LANGUAGE BangPatterns #-}
import Data.List
import Data.Maybe
import Data.Function (fix)
import Data.Array (Array, array, (!))
import qualified Data.ByteString as BS
import qualified Data.ByteString.Char8 as BS8
 
getInts :: IO [Int]
getInts = (map parseInt . BS8.words) <$> BS.getLine 
    where parseInt = fst . fromJust . BS8.readInt

solve :: String -> Int -> String
solve ('d':'r':'e':'a':'m':other) _ = solve other 1
solve ('e':'r':'a':'s':'e':other) _ = solve other 2
solve ('e':'r':'d':'r':'e':'a':'m':other) 1 = solve other 1
solve "er" 1 = "YES"
solve "r" 2 = "YES"
solve [] _ = "YES"
solve _ _ = "NO"

main :: IO ()
main = do
    str <- getLine
    putStrLn $ solve str 0