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 3.0.4) (judge verdict: Wrong Answer)

var
  s,t:ansistring;
begin
  readln(s);
  t:='';
  while (s<>'') do begin
    if (pos('dreameraser',s)=1) then 
      delete(s,1,11)
     else if (pos('dreamer',s)=1) then
      delete(s,1,7)
    else if (pos('eraser',s)=1) then
      delete(s,1,6)
    else if (pos('dream',s)=1) then
      delete(s,1,5)
      else if (pos('erase',s)=1) then
      delete(s,1,5)
    else begin
      writeln('NO');
      exit;
    end;
  end;
  writeln('YES');
end.