The three children are standing on and by a fence.
Three children are snowboarding.
The children cannot be standing on a fence while snowboarding at the same time.
exists e2 e1 x1 x2 x3.(n_child(x1) & card_eq_3(x1) & by(e2,x3) & n_fence(x3) & Actor(e2,x1) & v_stand(e2) & on(e1,x2) & n_fence(x2) & Actor(e1,x1) & v_stand(e1))
exists e1 x1.(Actor(e1,x1) & v_snowboard(e1) & n_child(x1) & card_eq_3(x1))