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: Wrong Answer)

program task_C;
    const A='dream';
    const B='dreamer';
    const C='erase';
    const D='eraser';
    var S:string;
    function delete(_:string;_l:integer):boolean;
    begin
        if _l=0 then exit(true);
        if Copy(_,_l-4,5)=A then delete:=delete(Copy(_,1,_l-5),_l-5)
        else if Copy(_,_l-5,6)=B then delete:=delete(Copy(_,1,_l-6),_l-6)
        else if Copy(_,_l-4,5)=C then delete:=delete(Copy(_,1,_l-5),_l-5)
        else if Copy(_,_l-5,6)=D then delete:=delete(Copy(_,1,_l-6),_l-6)
        else exit(false);
    end;
begin
    readln(S);
    if delete(S,length(S))=true then writeln('YES') else writeln('NO');
end.