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 Pascal (FPC 2.6.2) (judge verdict: Accepted)

program Project1;

{$APPTYPE CONSOLE}

uses
  SysUtils;
var
  s:string;
  i:Integer;
begin
  try
    { TODO -oUser -cConsole Main : ここにコードを記述してください }
    Readln(s);

    while True do    
      if (Copy(s,length(s)-6,7)='dreamer') then
        Delete(s,length(s)-6,7)
      else if (Copy(s,length(s)-5,6)='eraser') then
        Delete(s,length(s)-5,6)
      else if (Copy(s,length(s)-4,5)='dream')or(Copy(s,length(s)-4,5)='erase') then
        Delete(s,length(s)-4,5)
      else if s='' then begin
        Writeln('YES');
        break;
      end else begin
        Writeln('NO');
        break;
      end;

    Readln;
  except
    on E: Exception do
      Writeln(E.ClassName, ': ', E.Message);
  end;
end.