A skateboarder wearing a gray helmet is riding his board along a concrete curve.
A skateboarder is sitting on the bus.
One skateboarder cannot be riding his board while sitting on the bus.
exists e1 e2 s1 s2 x1 x2 x3 x4 x5.(along(e2,x5) & n_curve(x5) & a_concrete(s2) & Theme(s2,x5) & Theme(e2,x4) & Actor(e2,x1) & v_ride(e2) & n_board(x4) & of(x4,x1) & n_male(x1) & Theme(e1,x3) & Actor(e1,x2) & v_wear(e1) & n_helmet(x3) & a_gray(s1) & Theme(s1,x3) & (x1 = x2) & n_skateboarder(x1))
exists e1 x1 x2.(n_bus(x2) & on(e1,x2) & Actor(e1,x1) & v_sit(e1) & n_skateboarder(x1))