Two teenage boys are walking together down the sidewalk in a city.
Nobody is walking
Nobody walking contradicts Boys are walking.
exists e1 s1 x1 x2 x3 x4.(n_sidewalk(x3) & down(e1,x3) & in(x3,x4) & n_city(x4) & a_together(s1) & Manner(e1,s1) & Actor(e1,x1) & v_walk(e1) & n_boy(x1) & of(x1,x2) & n_teenage(x2) & card_eq_2(x1))
-exists e1 x1.(Actor(e1,x1) & v_walk(e1) & n_person(x1))