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 Java8 (OpenJDK 1.8.0) (judge verdict: Memory Limit Exceeded)

import java.util.Scanner;

public class Main {

    static String []PARTS = {"dream","dreamer","erase","eraser"};
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        String input = sc.next();
        if(check(input)){
            System.out.println("YES");
        }
        else{
            System.out.println("NO");
        }
        sc.close();

    }

    private static boolean check(String s){
        boolean flag = true;
        if(s.equals("")) return flag;
        for(int i=0;i<PARTS.length;i++){
            if(s.endsWith(PARTS[i])){
                return check(s.substring(0,s.length()-PARTS[i].length()));
            }
        }
        return false;
    }

}