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;
	id:Longint;
begin
	readln(S);
	id:=length(S);
	while id>0 do begin
		if(id>=5)and(copy(S,id-4,5)='dream')then dec(id,5)else if(id>=7)and(copy(S,id-6,7)='dreamer')then dec(id,7)else if(id>=5)and(copy(S,id-4,5)='erase')then dec(id,5)else if(id>=6)and(copy(S,id-5,6)='eraser')then dec(id,6)else begin writeln('NO');exit;end;
	end;
	writeln('YES');
end.