People walking in a marathon.
People are running in a marathon.
Walking and running are different.
exists e1 x1 x2 x3.(a_topic(x1) & in(e1,x3) & n_marathon(x3) & Actor(e1,x2) & v_walk(e1) & (x1 = x2) & n_people(x1))
exists e1 x1 x2.(in(e1,x2) & n_marathon(x2) & Actor(e1,x1) & v_run(e1) & n_people(x1))