(1)

    Given this sort of dict (country:city-list):

{'Israel': ['Jerusalem', 'Tel Aviv'],
'USA': ['Boston', 'New York', 'Chicago'],
'China': ['Beijing', 'Shanghai']}

    Use a nested list comprehension to produce a list of
    tuples that look like (city, country).

(2) Write a function sums_to_n that takes an argument n,
    and returns all two-element tuples that sum to n.

    sums_to_n(5)

    [(0,5), (1,4), (2,3), (4,1), (5,0)]

(3) Produce a list of the unique octets (from
    the IP addresses) in mini-access-log.