A seagull is standing on a picnic table
There are no seagulls.
There cannot be seagulls and no seagulls at the same time.
exists e1 x1 x2 x3.(on(e1,x2) & n_table(x2) & of(x2,x3) & n_picnic(x3) & Actor(e1,x1) & v_stand(e1) & n_seagull(x1))
exists p1 x1.-exists x2.((x1 = x2) & n_seagull(x2))