reserve i,j,k,l for natural Number;
reserve A for set, a,b,x,x1,x2,x3 for object;
reserve D,D9,E for non empty set;
reserve d,d1,d2,d3 for Element of D;
reserve d9,d19,d29,d39 for Element of D9;
reserve p,q,r for FinSequence;

theorem Th14:
  len(p^<*a*>) = len p + 1
proof
  len(p^<*a*>) = len p + len <*a*> by FINSEQ_1:22;
  hence thesis by FINSEQ_1:39;
end;
