Three boys play in an unfinished building.
There are no boys
There can't be boys and no boys.
exists e1 s1 x1 x2.(in(e1,x2) & n_building(x2) & a_unfinished(s1) & Theme(s1,x2) & Actor(e1,x1) & v_play(e1) & n_boy(x1) & card_eq_3(x1))
exists p1 x1.-exists x2.((x1 = x2) & n_boy(x2))