People at a costume party.
People are naked
People at a costumer party, not naked.
exists s1 x1 x2.(a_topic(x1) & at(x1,x2) & n_party(x2) & a_costume(s1) & Theme(s1,x2) & n_people(x1))
exists s1 x1.(Theme(s1,x1) & a_naked(s1) & n_people(x1))