A line of people makes its way up the steps.
The people are walking on a flat surface
Steps are not flat surface.
exists e1 x1 x2 x3 x4.(n_step(x4) & Theme(e1,x3) & Actor(e1,x1) & v_make(e1) & up(x3,x4) & n_way(x3) & of(x3,x1) & n_thing(x1) & of(x1,x2) & n_people(x2) & n_line(x1))
exists e1 s1 x1 x2.(n_people(x1) & on(e1,x2) & n_surface(x2) & a_flat(s1) & Theme(s1,x2) & Actor(e1,x1) & v_walk(e1))