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: Time Limit Exceeded)

var s:string;
begin
readln(s);
while (length(s)<>0) and (pos('eraser',s)<>0) do delete(s,pos('eraser',s),6);
while (length(s)<>0) and (pos('dreamer',s)<>0) do delete(s,pos('dreamer',s),7);
while (length(s)<>0) and (pos('erase',s)<>0) do delete(s,pos('erase',s),5);
while (length(s)<>0) and (pos('dream',s)<>0) do delete(s,pos('dream',s),5);
if length(s)>0 then writeln('NO')
else writeln('YES'); end.