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 Ruby (2.3.3) (judge verdict: Accepted)

s=gets.chomp
t=[""]
(s.length).times do |i|
  t.length.times do |j|
    t[j]+=s[i]
    if t[j]=="dream"
      t<< ""
    elsif t[j]=="erase"
      t<< ""
    elsif t[j]=="dreamer"
      t[j]=""
    elsif t[j]=="eraser"
      t[j]=""
    elsif t[j][0]!=?d&&t[j][0]!=?e
      t[j]=nil
    elsif t[j].length==8
      t[j]=nil
    end
  end
  t.compact!
end
puts t.include?("")? :YES : :NO