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 Python (3.4.3) (judge verdict: Accepted)

s = input()
words_r = ['eraser', 'erase', 'dreamer', 'dream']
for word_r in words_r:
    s = s.replace(word_r, '')
    #コードの意味:
    #s.replace(p,q) :文字列sにpという文字があればそれを先頭から順にqに置換していく
    #sはwords_rに含まれる文字列を''に置換した文字列になる
    #->条件に合うならｓは最終的に''に,そうでないならそれ以外になる
if (len(s) > 0):
    print('NO')
else:
    print('YES')