reserve i for Nat, x,y for set;
reserve S for non empty non void ManySortedSign;
reserve X for non-empty ManySortedSet of S;

theorem
  for X being set, a1,a2,a3,a4,a5,a6 being object
  st a1 in X & a2 in X & a3 in X & a4 in X & a5 in X & a6 in X
  holds {a1,a2,a3,a4,a5,a6} c= X
  by ENUMSET1:def 4;
