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
ok = true
while !s.empty? do
  if s.end_with?("dream")
    s.slice!(s.length - 5, 5)
  elsif s.end_with?("dreamer")
    s.slice!(s.length - 7, 7)
  elsif s.end_with?("erase")
    s.slice!(s.length - 5, 5)
  elsif s.end_with?("eraser")
    s.slice!(s.length - 6, 6)
  else
    ok = false
    break
  end
end
puts ok ? "YES" : "NO"