use std::collections::BinaryHeap;
use proconio::input;

fn main() {
    input! {
        n: usize,
        h: [usize; n],
    }

    let mut left = 0;
    let mut right = n + 1000;
    while right - left > 1 {
        let mid = (left + right) / 2;
        let mut h: BinaryHeap<usize> = h.iter().cloned().collect();

        for exp in (0..mid as u32).rev() {
            if h.len() == 0 {
                break;
            }

            if exp > 60 {
                h.pop();
            } else {
                let pop = h.pop().unwrap();

                if pop > 2usize.pow(exp) {
                    h.push(pop - 2usize.pow(exp));
                }
            }
        }

        if h.len() == 0 {
            right = mid;
        } else {
            left = mid;
        }
    }
    println!("{}", right);
}