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 taskd;
var s,s5,s6,s7,s10:string;
    process,i,j,len:longint;
begin
readln(s);
process:=1;
len:=Length(s);
while process<len do
begin
  s5:=Copy(s,process,5);
  s6:=Copy(s,process,6);
  s7:=Copy(s,process,7);
  s10:=Copy(s,process,10);
  if (s7='dreamer') and (s10<>'dreamerase') then
  process:=process+7
  else if s6='eraser' then
  process:=process+6
  else if (s5='dream') or (s5='erase') then
  process:=process+5
  else
  break;
end;
if process<=len then
writeln('NO')
else
writeln('YES');
end.