three people stand on the sidewalk.
Nobody is standing.
There can be three people or nobody standing.
exists e1 x1 x2.(n_sidewalk(x2) & on(e1,x2) & Actor(e1,x1) & v_stand(e1) & n_people(x1) & card_eq_3(x1))
-exists e1 x1.(Actor(e1,x1) & v_stand(e1) & n_person(x1))