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)

var s,t:ansistring;
i,j,k,l,m,n:longint;
begin
        readln(s);
        n:=length(s);
        for i:=1 to n do
        begin
                t:=t+s[i];
                if (t='dream') then t:=''
                else if (t='dreamer') then t:=''
                else if (t='erase') then t:=''
                else if (t='eraser') then t:=''
                else if (length(t)>=7) or (i=n) then
                begin
                        writeln('NO');
                        halt;
                end;
        end;
        writeln('YES');
end.