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 Rust (1.42.0) (judge verdict: Accepted)

use proconio::{fastout, input};

#[fastout]
fn main() {
    input! {
        s: String,
    }
    // annotate for rust-analyzer
    let mut s: &str = &s;

    let mut r = "YES";
    while s.len() > 0 {
        s = match s {
            e if e.ends_with("dream") => &s[..(s.len() - 5)],
            e if e.ends_with("dreamer") => &s[..(s.len() - 7)],
            e if e.ends_with("erase") => &s[..(s.len() - 5)],
            e if e.ends_with("eraser") => &s[..(s.len() - 6)],
            _ => {
                r = "NO";
                break;
            }
        };
    }

    println!("{}", r);
}