A boy is doing a skateboard trick on the railing of the steps.
a boy shows his brother a skateboard trick
If a boy does skateboarding, it doesn't mean he shows his brother a trick.
exists e1 x1 x2 x3 x4 x5.(n_step(x5) & n_railing(x4) & Theme(e1,x2) & Actor(e1,x1) & v_do(e1) & on(x2,x4) & of(x4,x5) & n_trick(x2) & of(x2,x3) & n_skateboard(x3) & n_boy(x1))
exists x1 x4.(all x2 x3.((n_trick(x2) & of(x2,x3) & n_skateboard(x3)) -> exists e1.(Theme(e1,x4) & Actor(e1,x1) & v_show(e1) & for(x4,x2))) & n_brother(x4) & of(x4,x1) & n_male(x1) & n_boy(x1))