{ Delphi }

//
// Problem  : Chain
// Contest  : UOI-2007 (Kremenchug)
// Type     : Solution
// Date     : March, 28th, 2007
// Version  : 1.0
// Author   : Andriy Stasyuk
// Language : Pascal
// Compiler : Delphi 7
// Algorithm: Author Solution
//

program chain;

{$APPTYPE CONSOLE}

var
  f: text;
  N, M, pow2: Int64;

begin
  assign(f, 'chain.dat');
  reset(f);
  readln(f, N);
  close(f);

  M := 0;
  pow2 := 2;
  while N > pow2 * (M+1) - 1 do
  begin
    pow2 := pow2 * 2;
    M := M + 1;
  end;

  assign(f, 'chain.sol');
  rewrite(f);
  writeln(f, M);
  close(f);
end.