using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace template
{
    class Program
    {
        static void Main(string[] args)
        {
            long n = long.Parse(Console.ReadLine());
            int ret = 0;
            for (long i = 1; i < n; i *= 2) ret++;
            Console.WriteLine(ret);
        }
    }
}