let ( @>> ) num i = Int64.shift_right num i
let ( @<< ) num i = Int64.shift_left num i
let ( @- ) num i = Int64.sub num i
let ( @= ) x y = (Int64.compare x y) = 0

let countBinNumDigits num =
	let rec countBinNumDigits' num result =
		if num @= Int64.zero then result
		else
			let nextNum, nextResult =
				num @>> 1, result + 1
			in
			countBinNumDigits' nextNum nextResult
	in
	countBinNumDigits' num 0

let countHit num =
	let cntHit = (countBinNumDigits num) - 1 in
	let rem = num @- (Int64.one @<< cntHit) in
  	if rem @= Int64.zero then cntHit else cntHit + 1
  	
let () =
	let num = read_line () |> Int64.of_string in
	countHit num |> string_of_int |> print_endline