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
s:string;
i:longint;
begin
readln(s);
while i<length(s) do
begin
if copy(s,i+1,11)='dreameraser' then i:=i+11
else if copy(s,i+1,10)='dreamerase' then i:=i+10
else if copy(s,i+1,6)='eraser' then i:=i+6
else if copy(s,i+1,5)='erase' then i:=i+5
else if copy(s,i+1,7)='dreamer' then i:=i+7
else if copy(s,i+1,5)='dream' then i:=i+5
else begin writeln('NO'); halt; end;
end;
writeln('YES');
end.