import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.ArrayList;

public class No47 {

	public static void main(String[] args) throws IOException{
		//ポケットを叩くとビスケットが2倍
		int N = Integer.parseInt(readStr()[0]) , s = 1 , count = 0;
		do {
			s = Math.min(s * 2, N);
			count += (s != 1 ? 1 : 0);
		}while(s < N);
		
		System.out.println(count);

	}
	
	public static String[] readStr() throws IOException{
		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
		ArrayList<String> list = new ArrayList<>();

		do {
			list.add(br.readLine());
		}while(br.ready());

		br.close();

		String[] text = new String[list.size()];
		list.toArray(text);

		return text;

	}

}