function solve(input) {
    let users = [];
    let articles = [];
    for (let i = 0; i < input.length; i++) {
        if (input[i].includes('article')) {
            let article = input[i].split(' ')[1];
            articles.push(article);
            delete input[i];
        } else if (input[i].includes('user')) {
            let user = input[i].split(' ')[1];
            users.push(user);
            delete input[i];
        }
    }
    let comments = new Map();
    for (let e of input) {
        if (e !== undefined) {
            let tokens = e.split(': ');
            let user = tokens[0].split(' ')[0];
            let article = tokens[0].split(' ')[3];
            let commentContent = tokens[1].split(', ').join(' - ');

            if (users.includes(user) && articles.includes(article)) {
                let contentString = '--- From user ' + (user) + ': ' + (commentContent);

                if (!comments.has(article)) {
                    comments.set(article, []);
                }
                comments.get(article).push(contentString);
            }
        }
    }

    let sortedComments = [...comments.entries()]
    .sort((a, b) => b[1].length - a[1].length);

    for(let e of sortedComments){
        let article = e[0];
        let comments = e[1].sort((a, b) => a.localeCompare(b));
        console.log(`Comments on ${article}`);
        for(let el of comments){
            console.log(`${el}`);
        }
    }
}

solve(['user aUser123',
    'someUser posts on someArticle: NoTitle, stupidComment',
    'article Books',
    'article Movies',
    'article Shopping',
    'user someUser',
    'user uSeR4',
    'user lastUser',
    'uSeR4 posts on Books: I like books, I do really like them',
    'uSeR4 posts on Movies: I also like movies, I really do',
    'someUser posts on Shopping: title, I go shopping every day',
    'someUser posts on Movies: Like, I also like movies very much'
]);