use proconio::{fastout, input};
use std::cmp::Ordering;

#[fastout]
fn main() {
    input! {n: usize, v: [f64; n]};

    let mut v: Vec<f64> = v;
    v.sort_by(cmp_f64);

    while v.len() > 1 {
        let m1 = v.pop().unwrap();
        let m2 = v.pop().unwrap();
        v.push((m1 + m2) / 2.0);
        v.sort_by(cmp_f64);
    }

    println!("{}", v[0]);
}

fn cmp_f64(a: &f64, b: &f64) -> Ordering {
    if a < b {
        return Ordering::Less;
    } else if a > b {
        return Ordering::Greater;
    }
    return Ordering::Equal;
}
