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 len(s) > 0:
    if s.startswith("dreamera"):
        s = s[5:]
        #print(s)
    elif s.startswith("eraser"):
        s = s[6:]
        #print(s)
    elif s.startswith("dreamer"):
        s = s[7:]
    elif s.startswith("dream"):
        s = s[5:]
    elif s.startswith("erase"):
      	s = s[5:]
    else:
        #print(s)
        print("NO")
        exit()
print("YES")