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: Time Limit Exceeded)

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

    if(check(S))
        println("YES")
    else
        println("NO")
}

fun check(s:String) : Boolean
{
    var result : Boolean = false

    if(s == "dreamer" || s == "dream" || s == "erase" || s == "eraser")
        return true
        else {
            if(s.startsWith("dreamer") || s.startsWith("dream") || s.startsWith("erase") || s.startsWith("eraser"))
            {
                if(check(s.substring(7))) return true
                if(check(s.substring(5))) return true
                if(check(s.substring(5))) return true
                if(check(s.substring(6))) return true
            } 
        return false
    }
}