Three people are standing at a concession stand outside.
Nobody is at the concession stand.
Either there is nobody there or there are three people there. It can't be both simultaneously.
exists e1 s1 x1 x2 x3.(a_outside(s1) & Manner(e1,s1) & at(e1,x2) & n_stand(x2) & of(x2,x3) & n_concession(x3) & Actor(e1,x1) & v_stand(e1) & n_people(x1) & card_eq_3(x1))
exists x2 x3.(n_stand(x2) & of(x2,x3) & n_concession(x3) & -exists p1 x1.(at(x1,x2) & n_person(x1)))