package main

import "fmt"
import "strings"

func main() {
	var n int64
	fmt.Scanf("%v", &n)
	b := fmt.Sprintf("%b", n)
	l := len(b)
	if strings.Contains(b, strings.Repeat("0", len(b)-1)) {
		l = l - 1
	}
	fmt.Printf("%d\n", l)
}