maxCost(10).
numCities(20).

adjacency(1,[10]).
adjacency(2,[7,5,17]).  % Three one-way roads from city 2:  2->7, 2->5 and 2->17.
adjacency(3,[6,20,11]).
adjacency(4,[14,15,1,8,5]).
adjacency(5,[16,4,9,10,11]).
adjacency(6,[1,13,17]).
adjacency(7,[16,9,13,11]).
adjacency(8,[7,3,10,6,17]).
adjacency(9,[6,17,11]).
adjacency(10,[7,11,5,6,4]).
adjacency(11,[20,8,15,4,1,16,3]).
adjacency(12,[15,11,3]).
adjacency(13,[5,2,19,3,6]).
adjacency(14,[10,12,9,7]).
adjacency(15,[20,1,14,18,12,2]).
adjacency(16,[7,6,4,8,2,10]).
adjacency(17,[20,5,16,3,8]).
adjacency(18,[15,16,7,14,3]).
adjacency(19,[13,6]).
adjacency(20,[12,6,18,7,16]).