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: Accepted)

fun main(args: Array<String>) {
    val input = readLine()!!.reversed()
    val words = listOf("dream", "dreamer", "erase", "eraser").map(String::reversed)
    val wl = words.map{it to it.length}
    var position = 0
    val len = input.length
    var ret = true
    loop@ while(position < len){
        for((w, l) in wl){
            if(position + l < len + 1 && input.substring(position, position + l) == w){
                position += l
                continue@loop
            }
        }
        ret = false
        break@loop
    }
    print(if(ret)"YES" else "NO")
}