#[macro_export] macro_rules! setup { { mut $input:ident: SplitWhitespace $(,)? } => { use std::io::Read; let mut buf = String::new(); std::io::stdin().read_to_string(&mut buf).unwrap(); let mut $input = buf.split_whitespace(); }; } #[macro_export] macro_rules! parse_next { ($str_iter:expr) => { $str_iter.next().unwrap().parse().unwrap() }; } fn main() { setup! { mut input: SplitWhitespace }; let n: usize = parse_next!(input); let ans = match n { 1 => 0, _ => { let mut i = 1; loop { if (2 as usize).pow(i as u32) >= n { break (i - 1) + 1; } i += 1; } } }; println!("{}", ans); }