A couple are dancing while others are watching a concert in a bandstand.
Nobody is watching the concert.
Either there are people watching a concert or nobody watching a concert.
exists e1 p1 x1.(exists e2 x2 x3 x4.(in(e2,x4) & n_bandstand(x4) & Theme(e2,x3) & Actor(e2,x2) & v_watch(e2) & n_concert(x3) & -(x2 = x1) & n_person(x2)) & n_person(x1) & while(e1,p1) & Actor(e1,x1) & v_dance(e1) & n_couple(x1))
exists x2.(n_concert(x2) & -exists e1 x1.(Theme(e1,x2) & Actor(e1,x1) & v_watch(e1) & n_person(x1)))