function make_first_line(words, page_width) {
    let weight = -1;
    let accept = "";
    let leftover = [];
    for (let i = words; !is_empty_list(i); i = tail(i)) {
        weight = weight + head(i).length + 1;
        if (weight <= page_width) {
            if (!equal(i, words)) {
            accept = accept + " " + head(i);
            } else {
            accept = accept + head(i);
            }
        } else {
            leftover = (i);
            break;
        }
    }
    return pair(accept, leftover);
}

function make_lines(words, page_width) {
    const stack = make_first_line(words, page_width);
    if (is_empty_list(words)) {
        return [];
    } else {
        return pair(head(stack), make_lines(tail(stack), page_width));
    }
}

function tail_n_times(xs, n) {
    if (is_empty_list(xs)) {
        return xs;
    } else if (n <= 0) {
        return xs;
    } else {
        return tail_n_times(tail(xs), n - 1);
    }
}
//cuts away n heads

function copy_list_n_times(xs, n) {
    if (is_empty_list(xs)) {
        return xs;
    } else if (n <= 0) {
        return [];
    } else {
        return pair(head(xs), copy_list_n_times(tail(xs), n - 1));
    }
}
//extracts first n part of list

function make_pages(lines, page_height) {
    if (is_empty_list(lines)) {
        return [];
    } else {
        return pair(copy_list_n_times(lines, page_height), make_pages(
                            tail_n_times(lines, page_height), page_height));
    }
}


function page_format(words, page_width, page_height) {
    return make_pages(make_lines(words, page_width), page_height);
}