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 JavaScript (node.js v5.12) (judge verdict: Accepted)

"use strict"

function Main(input) {
  const reverse = (s) => {
    return s.split('').reverse().join('');
  };

  const WORDS = ['dream', 'dreamer', 'erase', 'eraser'].map(reverse);
  const S = reverse(input.split('\n')[0]);

  let index = 0;

  while (true) {
    let w = WORDS.find((w) => S.startsWith(w, index));
    if (!w) break;
    index += w.length;
  }

  if (S.length === index) {
    console.log('YES');
  } else {
    console.log('NO');
  }
}

//*この行以降は編集しないでください（標準入出力から一度に読み込み、Mainを呼び出します）
Main(require("fs").readFileSync("/dev/stdin", "utf8"));