People are upside-down on a roller coaster.
Some people are in a roller coaster.
Some people in a roller coaster are upside down.
exists s1 x1 x2 x3.(on(s1,x2) & n_coaster(x2) & of(x2,x3) & n_roller(x3) & Theme(s1,x1) & a_upside-down(s1) & n_people(x1))
exists p1 x1.(exists x2 x3.(in(x1,x2) & n_coaster(x2) & of(x2,x3) & n_roller(x3)) & n_people(x1))