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 (3.8.2) (judge verdict: Accepted)

def solve():
    S = input()[::-1]
    i = 0
    while i < len(S):
        if S[i:i+5] in ['maerd', 'esare']:
            i += 5
        elif S[i:i+6] == 'resare':
            i += 6
        elif S[i:i+7] == 'remaerd':
            i += 7
        else:
            return 'NO'
    return 'YES'

    
if __name__ == '__main__':
    ans = solve()
    print(ans)