begin%tt%
go(city1, t1, city2, t2):- city1=1, city2=2, t2-t1>=60.
go(city1, t1, city2, t2):- city1=1, city2=3, t2-t1>=650.
go(city1, t1, city2, t2):- city1=1, city2=4, t2-t1>=400.
go(city1, t1, city2, t2):- city1=3, city2=5, t2-t1>=370.
go(city1, t1, city2, t2):- city1=4, city2=5, t2-t1>=600.
go(city1, t1, city2, t2):- city1=4, city2=6, t2-t1>=180.
go(city1, t1, city2, t2):- city1=2, city2=6, t2-t1>=150.
go(city1, t1, city2, t2):- city1=6, city2=5, t2-t1>=800.
go(city1, t1, city2, t2):- city1=2, city2=1, t2-t1>=60.
go(city1, t1, city2, t2):- city1=3, city2=1, t2-t1>=650.
go(city1, t1, city2, t2):- city1=4, city2=1, t2-t1>=400.
go(city1, t1, city2, t2):- city1=5, city2=3, t2-t1>=370.
go(city1, t1, city2, t2):- city1=5, city2=4, t2-t1>=600.
go(city1, t1, city2, t2):- city1=6, city2=4, t2-t1>=180.
go(city1, t1, city2, t2):- city1=6, city2=2, t2-t1>=150.
go(city1, t1, city2, t2):- city1=5, city2=6, t2-t1>=800.

city(id, name):- id=1, name="Omaha".
city(id, name):- id=2, name="Lincoln".
city(id, name):- id=3, name="Minneapolis".
city(id, name):- id=4, name="Des_Moines".
city(id, name):- id=5, name="Chicago".
city(id, name):- id=6, name="Kansas_City".

go2(city1, t1, city2, t2):- go(id1, t1, id2, t2), city(id1, city1), city(id2, city2).
end%tt%                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                     