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)

def main():
    target = input()
    string = ["eraser", "dreamer", "erase", "dream"]
    for i in range(len(target)):
        for s in string:
            if target[-len(s):] == s:
                target = target[:-len(s)]
        if target == "":
            break
    print("YES" if target == "" else "NO")


if __name__ == '__main__':
    main()