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 Go (1.6) (judge verdict: Runtime Error)

package main

import "fmt"

func main() {
	var s string
	fmt.Scan(&s)
	var check bool
	for ;; {
		check = true
		if len(s) == 0 {
			fmt.Println("YES")
			break
		}
		if len(s) < 5 || len(s) == 8 || len(s) == 9{
			fmt.Println("NO")
			break
		}
		if s[0:5] == "dream" {
			if len(s) == 5 || s[5:6] == "d" {
				s = s[5:]
				check = false
			} else if len(s) >= 7 && s[5:7] == "er" {
				if len(s) == 7 || s[7:8] == "d" || s[7:8] == "e" {
					s = s[7:]
					check = false
				} else if s[7:8] == "a" {
					s = s[5:]
					check = false
				}
			}
		} else if s[0:5] == "erase" {
			check = false
			if len(s) == 5 {
				s = s[5:]
			}
			if s[5:6] == "r" {
				s = s[6:]
			} else {
				s = s[5:]
			}
		}
		if check {
			fmt.Println("NO")
			break
		}
	}
}