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
m,n,i,j,k,x,y,z:longint;
s,t:ansistring;
begin
    readln(s);
    while true do
    begin

        m:=pos('eraser',s);
        if m=0 then break else
        delete(s,m,6);
    end;
    while true do
    begin

        m:=pos('dreamer',s);
        if m=0 then break else
        delete(s,m,7);
    end;
    while true do
    begin

        m:=pos('dream',s);
        if m=-0 then break else
        delete(s,m,6);
    end;
    while true do
    begin

        m:=pos('erase',s);
        if m=-0 then break else
        delete(s,m,5);
    end;
    if length(s)=0 then writeln('YES') else writeln('NO');
end.