Stairs crowded with several people
A group of people are sitting on a bench.
If people are on the stairs, they're not sitting on a bench; and while it's possible that people might sit on stairs, it's unlikely that anyone would be sitting on crowded stairs.
exists e1 s1 x1 x2.(ne_nam_stairs(x1) & with(e1,x2) & n_people(x2) & a_several(s1) & Theme(s1,x2) & Actor(e1,x1) & v_crowd(e1))
exists e1 x1 x2 x3.(on(e1,x3) & n_bench(x3) & Actor(e1,x1) & v_sit(e1) & of(x1,x2) & n_people(x2) & n_group(x1))