A young man is' heading' a ball while on the beach, another young man, in the background, looks at him.
There is only one person on the beach.
If there is only one person on the beach there is no man in the background.
exists p1 s1 s2 x1 x7 x8.(n_beach(x8) & n_background(x7) & exists x2 x3.((x1 = x2) & all x4.(n_ball(x4) -> exists e1 p2 x5.(exists e2 s3 x6.(on(e2,x8) & at(e2,x1) & Actor(e2,x6) & v_look(e2) & in(x6,x7) & n_man(x6) & a_young(s3) & Theme(s3,x6) & -(x6 = x1)) & while(e1,p2) & Theme(e1,x5) & Actor(e1,x3) & v_head(e1) & for(x5,x4) & n_'(x5))) & (x2 = x3) & n_'(x2)) & n_male(x1) & n_man(x1) & n_man(x1) & a_young(s2) & Theme(s2,x1) & a_young(s1) & Theme(s1,x1))
exists p1 x1 x3.(n_beach(x3) & exists x2.((x1 = x2) & on(x2,x3) & n_person(x2) & card_eq_1(x2) & r_only(x2)))