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()
while 1:
    l=len(S)
    if S[-7:]   =="dreamer":
        S=S[0:l-7]
    elif S[-5:] =="dream":
        S=S[0:l-5]
    elif S[-6:] =="eraser":
        S=S[0:l-6]
    elif S[-5:] =="erase":
        S=S[0:l-5]
    else:break
if S=="":
    print("YES")
else:
    print("NO")