People climbing up stairs with graffiti behind them.
People climb down stairs in a pristine city.
People cannot be climbing up stairs simultaneously with climb down stairs. Graffiti is not an attribute of a pristine city.
exists e1 s1 x1 x2 x3 x4.(a_topic(x1) & behind(e1,x1) & n_thing(x1) & with(e1,x4) & n_graffitus(x4) & a_up(s1) & Manner(e1,s1) & Theme(e1,x3) & Actor(e1,x2) & v_climb(e1) & n_stair(x3) & (x1 = x2) & n_people(x1))
exists e1 s1 s2 x1 x2 x3.(a_down(s2) & Manner(e1,s2) & Theme(e1,x2) & Actor(e1,x1) & v_climb(e1) & in(x2,x3) & n_city(x3) & a_pristine(s1) & Theme(s1,x3) & n_stair(x2) & n_people(x1))