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 Kotlin (1.0.0) (judge verdict: Memory Limit Exceeded)

fun main(args: Array<String>){
    val s = readLine()!!

    fun search(sub: String): Boolean {
        if(s == sub){
            return true
        }
        if(sub.length > s.length){
            return false
        }
        return search(sub + "dream") ||
        search(sub + "dreamer") ||
        search(sub + "erase") ||
        search(sub + "eraser")
    }

    println(if(search("")) "YES" else "NO")
}