Three people walk on grass adjacent to a river.
Both men and women are walking together.
Because there are both men and women, there must be more than three people. Just because there are three people does not mean there are both men and women.
exists e1 s1 x1 x2 x3 x4.(on(e1,x2) & to(s1,x4) & n_river(x4) & Theme(s1,x3) & a_adjacent(s1) & (x2 = x3) & n_grass(x2) & Actor(e1,x1) & v_walk(e1) & n_people(x1) & card_eq_3(x1))
exists e1 s1 x1 x2 x3.(n_woman(x3) & n_man(x2) & subset_of(x3,x1) & subset_of(x2,x1) & a_together(s1) & Manner(e1,s1) & Actor(e1,x1) & v_walk(e1))