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)

#!/usr/bin/env python3
import sys
sys.setrecursionlimit(300000)

YES = "YES"  # type: str
NO = "NO"  # type: str

def solve(S: str):
    elms = ['dream', 'dreamer', 'erase', 'eraser']
    while S:
        found = False
        for e in elms:
            if S[-len(e):] == e:
                found = True
                S = S[:-len(e)]
                break
        if not found:
            print(NO)
            return
    print(YES)
    return


def main():
    def iterate_tokens():
        for line in sys.stdin:
            for word in line.split():
                yield word
    tokens = iterate_tokens()
    S = next(tokens)  # type: str
    solve(S)

if __name__ == '__main__':
    main()