Four people are on a ski slope.
The four people are friends.
Four people together does not imply they are friends.
exists p1 x1.(exists x2 x3.(on(x1,x2) & n_slope(x2) & of(x2,x3) & n_ski(x3)) & n_people(x1) & card_eq_4(x1))
exists p1 x1.(n_people(x1) & card_eq_4(x1) & exists x2.((x1 = x2) & n_friend(x2)))