These people are walking on cement blocks.
The people are on a couch.
Couches are not made of cement blocks.
exists e1 x1 x2 x3.(n_people(x1) & on(e1,x2) & n_block(x2) & of(x2,x3) & n_cement(x3) & Actor(e1,x1) & v_walk(e1))
exists p1 x1.(n_people(x1) & exists x2.(on(x1,x2) & n_couch(x2)))