#include<bits/stdc++.h>
using namespace std;
using i64 = int64_t;

constexpr double eps = 1e-6;

void solve() {
    i64 n, k;
    cin >> n >> k;
    vector<i64> a(n + 1);
    for (int i = 1; i <= n; i++) {
        cin >> a[i];   
    }

    auto check = [&](double x) -> bool {
        set<double> st;
        st.insert(0);
        unordered_map<double, int> pos;
        pos[0] = 0;
        vector<int> f(n + 1);
        vector<double> b(n + 1);
        for (int i = 1; i <= n; i++) {
            b[i] = a[i] - x;
            b[i] += b[i - 1];
            auto p = st.upper_bound(b[i]);
            if (p != st.begin()) {
                f[i] = f[pos[*prev(p)]] + 1;
                st.insert(b[i]);
                pos[b[i]] = i;
            }
        }
        return f[n] >= k;
    };

    double l = 1;
    double r = *max_element(a.begin() + 1, a.end());
    double ans = 1;
    while (r - l > eps) {
        double m = (l + r) / 2;
        if (check(m)) {
            ans = max(ans, m);
            l = m;
        } else {
            r = m;
        }
    }

    cout << fixed << setprecision(15) << ans;
}

int main() {
    ios::sync_with_stdio(false);
    cout.tie(0);
    cin.tie(0);

    int T = 1;
    // cin >> T;
    for (int i = 1; i <= T; i++) {
        solve();
    }

    return 0;
}