use std::io::*;

fn check(x: f64, k: usize, a: &Vec<f64>) -> bool {
    let mut res = 0;
    for i in 0..a.len() {
        res += (a[i] / x) as usize;
    }
    return res >= k;
}

fn main() {
    let mut s: String = String::new();
    std::io::stdin().read_to_string(&mut s).ok();
    let mut itr = s.trim().split_whitespace();
    let n: usize = itr.next().unwrap().parse().unwrap();
    let a: Vec<f64> = (0..n)
        .map(|_| itr.next().unwrap().parse().unwrap())
        .collect();
    let k: usize = itr.next().unwrap().parse().unwrap();

    let mut l = 0.0;
    let mut r = 100000000000.0;
    for _ in 0..1000 {
        let mid = (l + r) / 2.0;
        if check(mid, k, &a) {
            l = mid;
        } else {
            r = mid;
        }
    }
    println!("{}", l);
}