reserve k,n for Nat,
  x,y,z,y1,y2 for object,X,Y for set,
  f,g for Function;
reserve p,q,r,s,t for XFinSequence;
reserve D for set;

theorem :: FINSEQ_1:13
  len(p|n) <= n
 proof
   Segm len(p|n) c= Segm n by RELAT_1:58;
  hence thesis by NAT_1:39;
 end;
