Boys outside a building.
Boys are sitting inside the lobby of the building.
There is a reference to boys outside a building which is contradictory of them sitting inside the lobby of the building.
exists x1 x2.(a_topic(x1) & outside(x1,x2) & n_building(x2) & n_boy(x1))
exists e1 x1 x2 x3.(n_building(x3) & n_lobby(x2) & inside(e1,x2) & of(x2,x3) & Actor(e1,x1) & v_sit(e1) & n_boy(x1))