B

module.exports = async function(input) {
    let files = [input];
    let result = [];

    let k = 0;
    while (k < files.length) {
        let src = files[k];
        k++;

        if (typeof (src) === Folder) {
            let size = src.size((size) => console.log(size));
            for (let i = 0; i < size; i++) {
                let dst = src.read(1, (file) => console.log(file));
                files.push(dst);
            }
        } else if (typeof(src) === String) {
            let p = '';
            for (let q of src) {
                if (q === p) {
                    result.push(src);
                    break;
                }
                p = q;
            }
        }
    }
    return result.sort();
}