 reserve x for Real,
    p,k,l,m,n,s,h,i,j,k1,t,t1 for Nat,
    X for Subset of REAL;

theorem
  for k being natural Number st k < 2 holds k = 0 or k = 1
proof
  let k be natural Number;
  assume k<2;
  then k<1+1;
  hence thesis by Th14,Th22;
end;
