let () =
  Printf.printf "Z.numbits 0 = %d\n" (Z.numbits Z.zero);
  Printf.printf "Z.numbits 1 = %d\n" (Z.numbits Z.one);
  Printf.printf "Z.numbits 2 = %d\n" (Z.numbits (Z.of_int 2));
  Printf.printf "Z.numbits 42 = %d\n" (Z.numbits (Z.of_int 42));
  Printf.printf "Z.numbits 6 = %d\n" (Z.numbits (Z.of_int 6));