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: Accepted)

package main

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

var rdr = bufio.NewReaderSize(os.Stdin, 1000000)

func readLine() []byte {
	buf := make([]byte, 0, 1000000)
	for {
		l, p, e := rdr.ReadLine()
		if e != nil {
			panic(e)
		}
		buf = append(buf, l...)
		if !p {
			break
		}
	}
	return buf
}

type TBytes []byte

func (obj TBytes) HasSuffix(keys []TBytes) int {
	for _, k := range keys {
		if bytes.HasSuffix(obj, k) {
			return len(k)
		}
	}
	return -1
}

func main() {
	s := TBytes(readLine())
	keys := []TBytes{TBytes("dreamer"), TBytes("eraser"), TBytes("dream"), TBytes("erase")}
	for klen := 0; klen >= 0; klen = s.HasSuffix(keys) {
		s = s[0 : len(s)-klen]
	}
	if len(s) == 0 {
		fmt.Println("YES")
	} else {
		fmt.Println("NO")
	}
}