Crowd of people hanging out on the stairs.
Some people on the stairs smoking.
Just because there are people hanging out on the stairs does is it mean that some of them are smoking.
exists e1 s1 x1 x2 x3 x4.(n_stair(x4) & a_topic(x1) & of(x1,x2) & a_out(s1) & Manner(e1,s1) & on(e1,x4) & Actor(e1,x3) & v_hang(e1) & (x2 = x3) & n_people(x2) & n_crowd(x1))
exists x1 x2 x3.(n_smoking(x2) & of(x2,x3) & n_stair(x3) & a_topic(x1) & on(x1,x2) & n_people(x1))