function bookShelf(input) {

    //let workInputArr = [...input];
    let bookShelf = {};
    // let iD;
    // let genre;
    // let author;
    // let bookName;

    input.forEach(line => {
        if (line.includes(' -> ')) {
            let [iD, genre] = line.split(' -> ');
            if (!bookShelf.hasOwnProperty(iD)) {
                bookShelf[iD] = { [genre]: [] };
            }
        } else {
            let [bookName, genre] = line.split(", ")
            for (let key in bookShelf) {
                if (bookShelf[key].hasOwnProperty(genre)) {
                    bookShelf[key][genre].push(bookName)
                    break;
                }
            }

        }

    })
    Object.keys(bookShelf).sort((a, b) => Object.entries(bookShelf[b])[0][1].length - Object.entries(bookShelf[a])[0][1].length)
        .forEach(id => {
            console.log(`${id} ${Object.keys(bookShelf[id])}: ${Object.values(bookShelf[id])[0].length}`);
            Object.values(bookShelf[id]).forEach(values => {
                values.sort((a, b) => a.localeCompare(b)).forEach(v => {
                    console.log(`--> ${v}`);
                });
            });
        });

//         if (line.includes(': ')) {
//             bookName = line.split(': ')[0];
//             let tokens = line.split(': ')[1];
//             [author, genre] = tokens.split(', ');
//             let isGenre = false;
//             Object.keys(bookShelf).forEach(shelf => {
//                 if (genre in bookShelf[shelf]) {
//                     isGenre = true;
//                     iD = shelf;
//                 }
//             });
//             if (isGenre) {
//                 bookShelf[iD][genre][bookName] = author;
//             }
//         }
//     });
// }


}