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 12.16.1) (judge verdict: Accepted)

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');
    }
}

main( require('fs').readFileSync('/dev/stdin', 'utf8') )