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 s = StringBuilder(readLine()!!)
    while (s.isNotEmpty()) {
        if (s.endsWith("dream")) {
            s.delete(s.length - 5, s.length)
        } else if (s.endsWith("dreamer")) {
            s.delete(s.length - 7, s.length)
        } else if (s.endsWith("erase")) {
            s.delete(s.length - 5, s.length)
        } else if (s.endsWith("eraser")) {
            s.delete(s.length - 6, s.length)
        } else {
            println("NO")
            return
        }
    }
    println("YES")
}