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.strip.reverse

d = ['dreamer', 'eraser', 'erase', 'dream'].map(&:reverse)

while true
        f = false
        d.each do |word|
                if s[-3, 3] == word[-3, 3]
                        s.slice!(word)
                        f = true
                        break
                end
        end
        if not f
                break
        end
end

if s == ""
        puts 'YES'
else
        puts 'NO'
end