A person is riding a bike on a shady sidewalk.
There are no sidewalks.
EITHER THE SIDEWALKS ARE THERE OR THERE IS NO SIDEWALK.
exists e1 s1 x1 x2 x3.(on(e1,x3) & n_sidewalk(x3) & a_shady(s1) & Theme(s1,x3) & Theme(e1,x2) & Actor(e1,x1) & v_ride(e1) & n_bike(x2) & n_person(x1))
exists p1 x1.-exists x2.((x1 = x2) & n_sidewalk(x2))