macro_rules! input {
    ($x:expr) => {
        let mut buf = String::new();
        std::io::stdin().read_line(&mut buf).unwrap();
        $x = buf.trim().parse().unwrap();
    };

    ($x:expr, $($y:expr), +) => {
        let mut buf = String::new();
        std::io::stdin().read_line(&mut buf).ok();
        input_iter!(buf.split_whitespace(), $x, $($y), +);
    };

    ($v:expr; $size:expr) => {
        let mut buf = String::new();
        std::io::stdin().read_line(&mut buf).ok();
        for v in buf.split_whitespace() {
            $v.push(v.parse().unwrap());
        }
    };

    ($v:expr; $h_size:expr, $w_size:expr) => {
        for _ in 0..$h_size {
            let mut part_vec = Vec::new();
            let mut buf = String::new();
            std::io::stdin().read_line(&mut buf).ok();
            for v in buf.split_whitespace() {
                part_vec.push(v.parse().unwrap());
            }
            $v.push(part_vec);
        }
    };
}

#[allow(unused_macros)]
macro_rules! input_iter {
    ($iter:expr, $x:expr) => {
        $x = $iter.next().unwrap().parse().unwrap();
    };

    ($iter:expr, $x:expr, $($y:expr), +) => {
        let mut iter = $iter;
        $x = iter.next().unwrap().parse().unwrap();
        input_iter!(iter, $($y), *);
    };
}

fn main() {
    let _n: i32;
    input!(_n);
    let mut v: Vec<i32> = Vec::new();
    input!(v; _n);
    v.sort();
    let mut cur: f32 = -1.0;
    for _v in v {
        if cur < 0.0 {
            cur = _v as f32;
            continue;
        }
        cur = (cur + _v as f32)/2.0;
    }
    print!("{}", cur);
}
