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)

program ABC049C;
uses StrUtils;
var
	T: array[0..3] of string = ('dream','dreamer','erase','eraser');
	s: string;
	i,c,l,k: integer;
begin
	for i:=0 to 3 do begin
		T[i]:=ReverseString(T[i]);
	end;
	readln(s);
	s:=ReverseString(s);
	c:=0;
	l:=Length(s);
	while c<l do begin
		k:=-1;
		for i:=0 to 3 do begin
			if copy(s,c+1,Length(T[i]))=T[i] then begin
				k:=Length(T[i]);
			end;
		end;
		if k<0 then begin
			writeln('NO');
			exit;
		end;
		c:=c+k;
	end;
	writeln('YES');
end.