def nonempty_region(r):
    """Return True if given region is nonempty.

    >>> nonempty_region([1,2,3,4,5,6])
    True
    >>> nonempty_region([1,2,4,4,5,6])
    False

    """
    assert type(r) == list
    assert len(r) == 6
    return (r[0] != r[1] and
            r[2] != r[3] and
            r[4] != r[5])