A group of people stand outside a bar at night.
Nobody is at the bar.
If a group of people is at the bar, there cannot be nobody there.
exists e1 x1 x2 x3 x4.(at(e1,x4) & n_night(x4) & outside(e1,x3) & n_bar(x3) & Actor(e1,x1) & v_stand(e1) & of(x1,x2) & n_people(x2) & n_group(x1))
exists x2.(n_bar(x2) & -exists p1 x1.(at(x1,x2) & n_person(x1)))