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 3.0.4) (judge verdict: Wrong Answer)

uses sysutils;
var s, tmp:ansistring;
    p:longint;
begin
    readln(s);
    p:=pos('dreameraser',s);
    writeln(p);
    while p<>0 do
    begin
        delete(s,p,11);
        p:=pos('dreameraser',s);
    end;
    p:=pos('dreamerase',s);
    writeln(p);
    while p<>0 do
    begin
        delete(s,p,10);
        p:=pos('dreamerase',s);
    end;
    p:=pos('dreamer',s);
    writeln(p);
    while p<>0 do
    begin
        delete(s,p,7);
        p:=pos('dreamer',s);
    end;
    p:=pos('eraser',s);
    writeln(p);
    while p<>0 do
    begin
        delete(s,p,6);
        p:=pos('eraser',s);
    end;
    p:=pos('erase',s);
    writeln(p);
    while p<>0 do
    begin
        delete(s,p,5);
        p:=pos('erase',s);
    end;
    p:=pos('dream',s);
    while p<>0 do
    begin
        delete(s,p,5);
        p:=pos('dream',s);
    end;
    if s='' then
        writeln('YES')
    else
        writeln('NO');
end.