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)

var n,i,j,k:longint;
s,c:ansistring;
begin
  readln(s);
  j:=length(s);
  i:=j;
  while ((i>=1) and (j-i<7)) do
    begin
      c:='';
      for k:=i to j do c:=c+s[k];
      if c='dream' then
        begin
          j:=i-1;
          i:=j;
        end
      else if c='erase' then
        begin
          j:=i-1;
          i:=j;
        end
      else if c='dreamer' then
        begin
          j:=i-1;
          i:=j;
        end
      else if c='eraser' then
        begin
          j:=i-1;
          i:=j;
        end
      else dec(i);
    end;
  if j=0 then writeln('YES') else writeln('NO');
end.