def to_str(card):
    """from card(int) to str
    >>> to_str(0)
    'S01'
    >>> to_str(1)
    'H01'
    >>> to_str(4)
    'S02'
    """
    num = to_num(card)
    suit = "CDHS"[card % 4]
    return "%s%02d" % (suit, num)

def to_num(card):
    return card / 4 + 1
    
def get_mid(*xs):
    """
    >>> get_mid(1, 5, 2)
    2
    >>> get_mid(1, 1, 1)
    1
    """
    if len(xs) == 1: xs = xs[0]
    assert len(xs) == 3
    return sorted(xs)[1]


def _test():    
    import doctest
    doctest.testmod()

if __name__ == "__main__":
    _test()