set(auto).

list(usable).

% An American who sells missiles to an unstable country is a criminal.

-american(x) | -sells(x, y, z) | -missile(y) | - unstable(z) | criminal(x).


% Smith sells missiles to North Korea.

sells(smith, m, north_korea).


% m is a missile

missile(m).


% North Korea is unstable

unstable(north_korea).


% Smith is an American

american(smith).


% Therefore smith is a criminal.

-criminal(smith).

end_of_list.