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: Wrong Answer)

S = gets.chomp.reverse
words = ["dream","dreamer","erase","eraser"].map(&:reverse)

def checker(words)
  dev = false
  words.map do |w1|
    s = S[0..w1.size - 1]
    if s == w1
      s = S[w1.size..-1]
      words.map do |w2|
        if s == w2
          dev = true
        end
      end
    end
  end
  return dev
end

puts checker(words) ? "YES" : "NO"