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 Julia (0.5.0) (judge verdict: Accepted)

function main()
  
  S_0 = split(chomp(readline()),"")
  reverse!(S_0)
  S = join(S_0)
  
  check = 0
  ans = true
  N = length(S)
  for i in 1:N
    
    if i <= check
      continue
    end
    
    if i+6 <= N && S[i:i+6] == "remaerd"
      check = i+6
    elseif i+5 <= N && S[i:i+5] == "resare"
      check = i+5
    elseif i+4 <= N && S[i:i+4] == "maerd"
      check = i+4
    elseif i+4 <= N && S[i:i+4] == "esare"
      check = i+4
    else
      ans = false
    end
    
  end
  
  if ans
    println("YES")
  else
    println("NO")
  end
  
end

main()