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 OCaml (4.02.3) (judge verdict: Accepted)

let rev s =
  let len = String.length s in
  let rec aux i acc =
    if i = len then acc else aux (i + 1) (Char.escaped s.[i] ^ acc)
  in
  aux 0 ""


let has_any_prefix s =
  try
    List.find
      (fun word ->
         let len = String.length word in
         try String.sub s 0 len = word with _ -> false)
      ["maerd"; "remaerd"; "esare"; "resare"]
  with Not_found -> ""


let trim_prefix s prefix =
  let len_pre = String.length prefix in
  let len_s = String.length s in
  String.sub s len_pre (len_s - len_pre)


let rec solve str =
  if String.length str = 0 then "YES"
  else
    match has_any_prefix str with
    | "" -> "NO"
    | a -> trim_prefix str a |> solve


let () = read_line () |> rev |> solve |> print_endline