use std::io;

fn main() {
    io::stdin().read_line(&mut String::new()).ok();

    let mut a = String::new();
    io::stdin().read_line(&mut a).ok();
    let mut a = a
        .split_whitespace()
        .map(|n| n.parse::<f64>().unwrap())
        .collect::<Vec<_>>();
    a.sort_unstable_by(|a, b| a.partial_cmp(b).unwrap());

    println!("{}", (a[(a.len() - 1) / 2] + a[a.len() / 2]) / 2f64);
}