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: Time Limit Exceeded)

var s,t,v,w:ansistring;
    a:array[1..4] of ansistring=('dreamer','eraser','dream','erase');
    i,j,k:longint;
begin
  readln(s);
  t:='';
  v:=s;
  for i:=1 to 4 do begin
    
    //writeln(s,' ',v,' ',w,' ',a[i]);
    if (pos(a[i],s)<>0) then begin
      for j:=1 to length(s) do
        delete(s,pos(a[i],s),length(a[i]));
        if (i=1) or (i=2) then delete(v,pos(a[i+2],v),length(a[i+2]));
        w:=v;
        for k:=1 to 4 do begin
          if (pos(a[k],w)<>0) then delete(w,pos(a[k],w),length(a[k]));
        end;
        if (w=t) then begin
          writeln('YES');
          exit;
        end;
    end;
  end;
  if (s<>t) and (v<>t) then writeln('NO')
  else writeln('YES');
end.