nchairs(4).
npersons(16).
table(1..4).
person(a).
person(b).
person(c).
person(d).
person(e).
person(f).
person(g).
person(h).
person(i).
person(j).
person(k).
person(l).
person(m).
person(n).
person(o).
person(p).
like(a,b).
like(c,b).
dislike(b,d).
like(e,d).
dislike(f,e).
like(i,f).
like(g,h).
dislike(k,l).
like(k,m).
dislike(p,o).
like(o,n).
at(P,T):- person(P), table(T), not not_at(P,T).
not_at(P,T):- person(P), table(T), not at(P,T).
:- table(T), nchairs(C), count({X,at(X,T)})>C.
:- person(P), count({X,at(P,X)})!=1.
:- table(T), like(P1,P2), at(P1,T), not at(P2,T).
:- table(T), dislike(P1,P2), at(P1,T), at(P2,T).