Four people sitting in branches on a tree.
The four people are friends.
Four people sitting together doesn't mean they're friends, or even know each other.
exists e1 x1 x2 x3 x4.(a_topic(x1) & on(e1,x4) & n_tree(x4) & in(e1,x3) & n_branch(x3) & Actor(e1,x2) & v_sit(e1) & (x1 = x2) & n_people(x1) & card_eq_4(x1))
exists p1 x1.(n_people(x1) & card_eq_4(x1) & exists x2.((x1 = x2) & n_friend(x2)))