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)

import java.io.InputStream
import java.io.PrintStream
import java.util.*

class Arc065A(
    val input: InputStream,
    val output: PrintStream
) {
    fun proc() {
        val sc = Scanner(input)
        var input = sc.nextLine()

        val strs = listOf("dream", "dreamer", "erase", "eraser")

        while (input.isNotEmpty()) {
            val a = strs.find { input.endsWith(it) }
            if (a == null) {
                output.print("NO")
                return
            }
            input = input.removeSuffix(a)
        }
        output.print("YES")
    }
}

fun main(args: Array<String>) {
    Arc065A(System.`in`, System.out).proc()
}