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 C++14 (GCC 5.4.1) (judge verdict: Wrong Answer)

#include <bits/stdc++.h>
using namespace std;


int main() {
  string S;
  cin >> S;
  
  while(S!=""){
  	if (S.substr(0,6)=="dreamer") S=S.substr(7);
    else if (S.substr(0,4)=="dream") S=S.substr(5);
    else if (S.substr(0,5)=="eraser") S=S.substr(6);
    else if (S.substr(0,4)=="erase") S=S.substr(5);
    else break;
  }
  
  if (S.size()) cout << "NO" << endl;
  else cout << "YES" << endl;
}