def calculate_score(points):
    """
    Assignment 3
    """
    result = ""
    data = {}
    gamers = set(x.lower() for x in points)

    for e, g in enumerate(gamers):
        data[g] = points.count(g) - points.count(g.upper())
    data = sorted(data.items(), key=lambda x: (x[1],x[0]), reverse=True)

    for d in data:
        result += d[0] + ':' +str(d[1]) + ', '

    return "%s" % result[:-2]