reserve x,y,z for set;
reserve f,f1,f2,f3 for FinSequence,
  p,p1,p2,p3 for set,
  i,k for Nat;
reserve D for non empty set,
  p,p1,p2,p3 for Element of D,
  f,f1,f2 for FinSequence of D;
reserve D for non empty set;
reserve p, q for FinSequence,
  X, Y, x, y for set,
  D for non empty set,
  i, j, k, l, m, n, r for Nat;
reserve a, a1, a2 for TwoValued Alternating FinSequence;
reserve fs, fs1, fs2 for FinSequence of X,
  fss, fss2 for Subset of fs;
reserve F, F1 for FinSequence of INT,
  k, m, n, ma for Nat;
reserve i,j,k,m,n for Nat,
  D for non empty set,
  p for Element of D,
  f for FinSequence of D;

theorem Th6:
  1 <= len (f:-p)
proof
  len(f:-p) = len(<*p*>^(f/^p..f)) by FINSEQ_5:def 2
    .= len<*p*> + len(f/^p..f) by FINSEQ_1:22
    .= 1 + len(f/^p..f) by FINSEQ_1:39;
  hence thesis by NAT_1:11;
end;
