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: Wrong Answer)

package main

import (
	"bufio"
	"fmt"
	"os"
)

func main() {
	scanner := bufio.NewScanner(os.Stdin)
	scanner.Scan()
	text := scanner.Text()

	ed := len(text)
	isYes := true
	for ed > 0 {
		if ed-5 >= 0 && (text[ed-5:ed] == "dream" || text[ed-5:ed] == "erase") {
			ed = ed - 5
		} else if ed-6 >= 0 && text[ed-6:ed] == "eraser" {
			ed = ed - 6
		} else if ed-7 >= 0 && text[ed-7:ed] == "dreamer" {
			ed = ed - 7
		} else {
			isYes = false
			break
		}
	}

	if isYes {
		fmt.Println("YES")
	} else {
		fmt.Println("NO")
	}
}