def contributors():
    last_post = "_posts/" + sorted(os.listdir("_posts"))[-1]

    with open(last_post) as f:
        text = f.read()

    names = sorted({n[2:-1] for n in re.findall(r"\[@[^]]+]", text)})

    with open(last_post) as f:
        old_text = f.read()

    with open(last_post, 'a') as f:
        f.write("\n")
        for name in names:
            line = contributor_url(name)
            if line not in old_text:
                f.write(line)