A man in a hat is sitting next to another man.
Nobody is sitting
Either a man is sitting or nobody is sitting.
exists e1 x1 x2 x3.(to(e1,x3) & n_man(x3) & -(x3 = x1) & n_man(x1) & n_man(x1) & r_next(e1) & Actor(e1,x1) & v_sit(e1) & in(x1,x2) & n_hat(x2))
-exists e1 x1.(Actor(e1,x1) & v_sit(e1) & n_person(x1))