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)

d = ["maerd", "remaerd", "esare", "resare"]
s = gets.chomp
s.reverse!
t = s.dup
while s do
  for i in 0..3
    if s.start_with?(d[i])
      #puts d[i]
      #puts s
      #puts t
      s.slice!(0, d[i].length)
      #puts s
      #puts t
    end
    #puts s
  end
  if s == ""
    #puts s
    puts "YES"
    exit
  end
  if s == t
    #puts s
    #puts t
    puts "NO"
    exit
  end
  #puts s
  #puts t
  t = s.dup
end