Two police officers are standing in uniform.
Nobody is standing
There cannot be both police officers standing and nobody standing at the same time.
exists e1 x1 x2 x3.(in(e1,x3) & n_uniform(x3) & Actor(e1,x1) & v_stand(e1) & n_officer(x1) & of(x1,x2) & n_police(x2) & card_eq_2(x1))
-exists e1 x1.(Actor(e1,x1) & v_stand(e1) & n_person(x1))