We got 6 couples: Aa Bb Cc Dd Ee Ff (Capitals = husbands).
They're all on one side of a river, and want to cross over.
The guys are terribly jealous and insist on always having
their wives by their sides; so a wife is always with her
husband, on either side of the river or in the boat, if
there is another guy around.
EXCEPTION to above:
F hates his wife and doesn't care which guy(s) she's with;
they really can't stand each other and don't want to be
in boat at same time, or on river banks while boat crosses.
F : I hate your guts, f !
f : I shudda listened to mudder and never marry ya, ya jerk !!
(You may wish to know that during my research for this
puzzle, I found out that F doubled the life insurance on f).
They have one boat; it's capacity is up to 3 persons.
A special boating license to drive boat is required;
only one of the husbands has one; sorry, forgot which husband.
Of the wives, only f has one: she just finished the boating
course and has been issued a temporary license:
good for 4 one-way crossings ONLY.
So, when boat is crossing, f and/or that licenced husband
must be in the boat.
What is the minimum number of one-way trips required to get
everybody across ?