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 : ansistring;
  
begin

  readln(S);

    while pos('dreamererase', S) <> 0 do
      delete(S, pos('dreamererase', S), 12);
      
    while pos('dreamereraser', S) <> 0 do
      delete(S, pos('dreamereraser', S), 13);
    
    while pos('dreameraser', S) <> 0 do
      delete(S, pos('dreameraser', S), 11);
      
    while pos('dreamerase', S) <> 0 do
      delete(S, pos('dreamerase', S), 10);

    while pos('dreamer', S) <> 0 do
      delete(S, pos('dreamer', S), 7);
      
    while pos('dream', S) <> 0 do
      delete(S, pos('dream', S), 5);
      
    while pos('eraser', S) <> 0 do
      delete(S, pos('eraser', S), 6);
    
    while pos('erase', S) <> 0 do
      delete(S, pos('erase', S), 5);
    
    if length(S) = 0 then
      writeln('YES')
    else
      writeln('NO');

end.