People are walk and running on a bridge sidewalk.
The people are on a stair.
People can be either on a bridge sidewalk or on a stair.
exists e1 e2 s1 x1 x2 x3 x4 x5.(a_topic(s1) & subset_of(e2,s1) & on(e2,x4) & n_sidewalk(x4) & of(x4,x5) & n_bridge(x5) & Actor(e2,x3) & v_run(e2) & n_thing(x3) & subset_of(x1,s1) & Theme(e1,x2) & v_walk(e1) & (x1 = x2) & n_people(x1))
exists p1 x1.(n_people(x1) & exists x2.(on(x1,x2) & n_stair(x2)))