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

using i64 = long long;

const int P = 1e9 + 7;
void add(int &x, int y) { (x += y) >= P && (x -= P); }

const int N = 200005;
int n, a[N], k;
double s[N], f[N];

bool check(double mid) {
    int top = 0;
    f[++top] = 0;
    for (int i = 1; i <= n; ++i) {
        s[i] = s[i - 1] + a[i] - mid;
        int pos = lower_bound(f + 1, f + top + 1, s[i]) - f;
        if (i == n) return pos > k;
        f[pos] = s[i];
        if (pos == top + 1) ++top;
    }
}

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

    cin >> n >> k;
    for (int i = 1; i <= n; ++i) cin >> a[i];

    double l = 1, r = 1000;
    for (int t = 0; t < 30; ++t) {
        double mid = (l + r) / 2;
        if (check(mid)) {
            l = mid;
        } else {
            r = mid;
        }
    }

    cout << setprecision(20) << l << "\n";

    return 0;
}