Four men are rollerskating in a line, with the last three holding onto the hips of the man ahead of them.
A group of men rollerskate in a worm/snake formation holding on to the man in front of them.
Four men is a group of men.  Are roller-skating is to roller-skate.  Holding onto the hips of th e man ahead is worm-snake formation.
exists e2 e1 s1 x1 x2 x3 x4.(n_hip(x3) & onto(e2,x3) & of(x3,x1) & of(x4,x1) & n_thing(x1) & ahead(x1,x4) & n_thing(x4) & n_man(x1) & n_man(x1) & Actor(e2,x1) & v_hold(e2) & with(e1,x1) & card_eq_3(x1) & a_last(s1) & Theme(s1,x1) & in(e1,x2) & n_line(x2) & Actor(e1,x1) & v_rollerskate(e1) & card_eq_4(x1))
exists e2 e1 x1 x2 x3 x4 x5 x6.(in(e1,x3) & in(e2,x6) & of(x6,x1) & n_thing(x1) & n_front(x6) & r_on(e2) & to(e2,x2) & n_man(x2) & n_man(x2) & Actor(e2,x5) & v_hold(e2) & (x3 = x5) & n_formation(x3) & of(x3,x4) & n_worm/snake(x4) & Actor(e1,x1) & v_rollerskate(e1) & of(x1,x2) & n_group(x1))