Problem:
Score : 300 points

Problem Statement

As a token of his gratitude, Takahashi has decided to give his mother an integer sequence.
The sequence A needs to satisfy the conditions below:

A consists of integers between X and Y (inclusive).

For each 1\leq i \leq |A|-1, A_{i+1} is a multiple of A_i and strictly greater than A_i.

Find the maximum possible length of the sequence.

Constraints

1 \leq X \leq Y \leq 10^{18}

All input values are integers.

Input

Input is given from Standard Input in the following format:

X Y

Output

Print the maximum possible length of the sequence.

Sample Input 1

3 20

Sample Output 1

3

The sequence 3,6,18 satisfies the conditions.

Sample Input 2

25 100

Sample Output 2

3

Sample Input 3

314159265 358979323846264338

Sample Output 3

31

Solution in Rust (1.15.1) (judge verdict: Accepted)

#!/usr/bin/env run-cargo-script

#![allow(unused_imports)]

use std::cmp;
use std::collections::{BTreeMap, BTreeSet, BinaryHeap, HashMap, HashSet, VecDeque};
use std::fmt;
use std::io::{self, BufWriter, Read, StdinLock, Write};
use std::ops::{Add, Div, Mul, Sub};
use std::str::{self, FromStr};

fn solve(mut x: u64, y: u64) -> u32 {
    let mut r = 0;
    while x <= y {
        x *= 2;
        r += 1;
    }
    r
}

fn main() {
    let stdin = io::stdin();
    let mut sc = Scanner::new(stdin.lock().bytes());
    println!("{}", solve(sc.next(), sc.next()));
}

struct Scanner<R: Read> {
    buf: Vec<u8>,
    bytes: io::Bytes<R>,
}

#[allow(dead_code)]
impl<R: Read> Scanner<R> {
    fn new(bytes: io::Bytes<R>) -> Self {
        Scanner {
            buf: Vec::with_capacity(1024),
            bytes: bytes,
        }
    }

    fn next<T: FromStr>(&mut self) -> T
    where
        <T as FromStr>::Err: fmt::Debug,
    {
        let buf = &mut self.buf;
        buf.clear();
        self.bytes
            .by_ref()
            .map(Result::unwrap)
            .skip_while(|&c| c == ' ' as u8 || c == '\n' as u8)
            .take_while(|&c| !(c == ' ' as u8 || c == '\n' as u8))
            .foreach(|c| buf.push(c));
        str::from_utf8(&buf).unwrap().parse().unwrap()
    }

    fn vec<T: FromStr>(&mut self, n: usize) -> Vec<T>
    where
        <T as FromStr>::Err: fmt::Debug,
    {
        (0..n).map(|_| self.next()).collect()
    }

    fn pairs<T1: FromStr, T2: FromStr>(&mut self, n: usize) -> Vec<(T1, T2)>
    where
        <T1 as FromStr>::Err: fmt::Debug,
        <T2 as FromStr>::Err: fmt::Debug,
    {
        (0..n).map(|_| (self.next(), self.next())).collect()
    }

    fn trios<T1: FromStr, T2: FromStr, T3: FromStr>(&mut self, n: usize) -> Vec<(T1, T2, T3)>
    where
        <T1 as FromStr>::Err: fmt::Debug,
        <T2 as FromStr>::Err: fmt::Debug,
        <T3 as FromStr>::Err: fmt::Debug,
    {
        (0..n)
            .map(|_| (self.next(), self.next(), self.next()))
            .collect()
    }

    fn mat<T: FromStr>(&mut self, m: usize, n: usize) -> Vec<Vec<T>>
    where
        <T as FromStr>::Err: fmt::Debug,
    {
        (0..m).map(|_| self.vec(n)).collect()
    }

    fn strings_as_mat<T, F: FnMut(u8) -> T>(&mut self, h: usize, mut f: F) -> Vec<Vec<T>> {
        (0..h)
            .map(|_| {
                self.bytes
                    .by_ref()
                    .map(Result::unwrap)
                    .skip_while(|&c| c == ' ' as u8 || c == '\n' as u8)
                    .take_while(|&c| !(c == ' ' as u8 || c == '\n' as u8))
                    .map(&mut f)
                    .collect()
            })
            .collect()
    }
}

trait Foreach {
    type Item;
    fn foreach<F: FnMut(Self::Item)>(self, f: F);
}

impl<T, I: Iterator<Item = T>> Foreach for I {
    type Item = T;

    fn foreach<F: FnMut(T)>(self, mut f: F) {
        self.fold((), move |(), x| f(x));
    }
}