> I haven't read the article

Well, you should've - it's very clearly explained:

    The text file has a simple structure with one measurement value per row:

        Hamburg;12.0
        Bulawayo;8.9
        Palembang;38.8
        St. John's;15.2
        Cracow;12.6
        ...

    The program should print out the min, mean, and max values per station, alphabetically ordered like so:

    {
        Abha=5.0/18.0/27.4,
        Abidjan=15.7/26.0/34.1,
        Abéché=12.1/29.4/35.6,
        Accra=14.7/26.4/33.1,
        Addis Ababa=2.1/16.0/24.3,
        Adelaide=4.1/17.3/29.7,
        ...
    }