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: Memory Limit Exceeded)

var
 n:ansistring;
procedure dfs(s:string);
begin
 if s='' then begin writeln('YES'); halt; end;
 if not((copy(s,1,5)='dream') or (copy(s,1,5)='erase')
    or (copy(s,1,7)='dreamer') or (copy(s,1,6)='eraser'))
     then exit;
 if copy(s,1,5)='dream' then dfs(copy(s,6,length(s)));
 if copy(s,1,5)='erase' then dfs(copy(s,6,length(s)));
 if copy(s,1,6)='eraser' then dfs(copy(s,7,length(s)));
 if copy(s,1,7)='dreamer' then dfs(copy(s,8,length(s)));
end;
begin
 readln(n);
 dfs(n);
 writeln('NO');
end.