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)

// ABC049

// inputに入力データ全体が入る
function Main(input) {
  var S = reverse(input.split("\n")[0].toString());
  const a = reverse("dream");
  const b = reverse("dreamer");
  const c = reverse("erase");
  const d = reverse("eraser");
  var flag = 0;
  var result = "YES";

  while(S.length > 0 && flag != 1) {
    if(!S.indexOf(a)){
      S = S.slice( a.length ) ;
    } else if(!S.indexOf(b)){
      S = S.slice( b.length ) ;
    } else if(!S.indexOf(c)){
      S = S.slice( c.length ) ;
    } else if(!S.indexOf(d)){
      S = S.slice( d.length ) ;
    } else {
      flag = 1;
      result = "NO";
    }
  }
  console.log(result);
}

// 文字逆さ
function reverse(s) {
  var tmp = s.split("");
  var str = "";
  for(var i=tmp.length-1;i>=0;i--) {
    str += tmp[i].toString();
  }
  return str;
}

Main(require("fs").readFileSync("/dev/stdin", "utf8"));