fn main() {
    let n: u32 = read();
    let c = (0..).map(|n|2u32.pow(n)).take_while(|&k|k<n).count();
    println!("{}", c);
}

fn read<T: std::str::FromStr>() -> T {
    let mut s = String::new();
    std::io::stdin().read_line(&mut s).ok();
    s.trim().parse().ok().unwrap()
}