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: Runtime Error)

s = gets

list = [
  "dream",
  "dreamer",
  "erase",
  "eraser",
]

while s.legth >0
  list.each do |w|
    if s[(s.length-w.length)..-1] == w
      s = s[-1..(s.length-w.length)]
    else
      puts "NO"
      exit
    end
  end
end
puts "YES"