Three workers are performing their jobs while on scaffolding.
Nobody is performing.
If three workers are performing their jobs, somebody is performing, not nobody.
exists e1 x1 x2 x3.(on(e1,x3) & n_scaffolding(x3) & r_while(e1) & Theme(e1,x2) & Actor(e1,x1) & v_perform(e1) & n_job(x2) & of(x2,x1) & n_thing(x1) & n_worker(x1) & card_eq_3(x1))
-exists e1 x1.(Actor(e1,x1) & v_perform(e1) & n_person(x1))