#include <bits/stdc++.h>
using namespace std;

const int N = 2e5 + 50;
using db = double;

int n, k;
int s[N];

bool check(db mid) {
    multiset<db> ss;
    ss.insert(0);
    db las = s[n] - mid * n;
    for (int i = 1; i < n; i++) {
        db x = s[i] - mid * i;
        if (x < 0) continue;
        if (x > las) continue;
        auto it = ss.lower_bound(x);
        if (it != ss.end())
            ss.erase(it);
        ss.insert(x);
    }
    return ss.size() >= k;
}

int main() {
    cin >> n >> k;
    for (int i = 1; i <= n; i++) {
        int x;
        scanf("%d", &x);
        s[i] = s[i - 1] + x;
    }

    db l = 0, r = 1000;
    for (int cnt = 1; cnt <= 100; cnt++) {
        db mid = (l + r) / 2;
        if (check(mid)) l = mid;
        else r = mid;
    }
    cout << fixed << setprecision(12) << l << "\n";
    return 0;
}