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

loop do
  if s[-5..-1] == 'dream' || s[-5..-1] == 'erase'
    s.slice!(-5..-1)
  elsif s[-6..-1] == 'eraser'
    s.slice!(-6..-1)
  elsif s[-7..-1] == 'dreamer'
    s.slice!(-7..-1)
  else
    puts 'NO'
    exit
  end
  if s.empty?
    puts 'YES'
    exit
  end
end