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: Wrong Answer)

function Main(input){
  var S = input.split('');
  var T = '';
  var length = S.length;
  
  if(length < 5){
    console.log('NO');
  } else {
    for(var i = 5; i <= length; i += 5){
      var str = S[i-5] + S[i-4] + S[i-3] + S[i-2] + S[i-1];
      if(str == 'dream'){
        if(i+2 < length){
          var a = S[i] + S[i+1] + S[i+2];
          if(a == 'era'){
            T = T + 'dream';
          } else {
            T = T + 'dreamer';
            i += 2;
          }
        } else if(i+1 < length){
          var a = S[i] + S[i+1];
          if(a == 'er'){
            T = T + 'dreamer';
            i += 2;
          } else {
            T = T + 'dream';
          }
        } else {
          T = T + 'dream';
        }
      } else if(str == 'erase'){
        if(i < length){
          if(S[i]== 'r'){
            T = T + 'eraser';
            i += 1;
          } else {
            T = T + 'erase';
          }
        } else {
          T = T + 'erase';
        }
      } else {
        break;
      }
    }
    
    if(T == S){
      console.log('YES');
    } else {
      console.log('NO');
    }
  }
}

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