songs = dict()

artists = open("artisti.txt", "r")

for artist in artists:
    artist = artist.split(";")
    artCode = artist[0].strip()

    songsFile = open(artist[1].strip(), "r")

    for song in songsFile:
        song = song.split(";", 1)
        year = song[0]
        title = song[1].strip()

        if year not in songs:
            songs[year] = []

        songs[year].append({"artist": artCode, "title": title})

    songsFile.close()

artists.close()

years = sorted(list(songs.keys()))

for year in years:
    print(year + ":")

    for s in songs[year]:
        print(s["title"] + "\t" + s["artist"])