Three men are working on a roof.
the men are in a boat.
A roof isn't a boat.
exists e1 x1 x2.(on(e1,x2) & n_roof(x2) & Actor(e1,x1) & v_work(e1) & n_man(x1) & card_eq_3(x1))
exists p1 x1.(n_man(x1) & exists x2.(in(x1,x2) & n_boat(x2)))