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

divides = ['dream', 'dreamer', 'erase', 'eraser']
dp = S.size.times.map{false}
dp[0] = true

0.step (S.size - 1) do |i|
  next if !dp[i]
  divides.each do |d|
    puts "#{i}: #{d}"
    dp[i + d.size] = true if S.slice(i, d.size) == d
  end
end
p dp
puts dp[S.size] ? 'YES' : 'NO'