2. Сложность двоичного поиска.

import java.io.*;
import java.util.*;

public class Main {
    public static void main(String args[]) {
        try (PrintWriter out = new PrintWriter(System.out)) {
            Scanner in = new Scanner(System.in);

            int n = in.nextInt();
            int x = 2;
            int res = 1;
            while (x < n) {
                x *= 2;
                res++;
            }
            out.print(res);
        } catch(Exception e) {
            System.out.println("Exception: " + e);
        }
    }
}