#include <bits/stdc++.h>
#define fir first
#define sec second
using namespace std;
using ll = long long;
using PII = pair<double, int>;
const int mod = 1000000007;
void solve()
{
	int n, k, sum = 0, mx = -1;
	cin >> n >> k;
	vector<int> a(n + 1, 0);
	for (int i = 1; i <= n; i++) {
		cin >> a[i];
		mx = max(mx, a[i]);
		sum += a[i];
	}
	function<bool(double)> check = [&](double ave) {
		vector<double> sum(n + 1, 0);
		vector<double> res(n + 1, 0);
		vector<int> ans(n + 1, 0);
		for (int i = 1; i <= n; i++) {
			res[i] = a[i] - ave;
			// cout << res[i] << " ";
		}
		// cout << endl;
		multiset<PII> s;
		s.insert(PII(0, 0));
		for (int i = 1; i <= n; i++) {
			sum[i] = sum[i - 1] + res[i];
			auto it = s.upper_bound(PII(sum[i], n + 1));
			if (it == s.begin()) {
				ans[i] = -1;
				continue;
			}
			it--;
			ans[i] = it->sec + 1;
			s.insert(PII(sum[i], ans[i]));
			it = ++s.find(PII(sum[i], ans[i]));
			while (it != s.end() && it->sec <= ans[i]) {
				auto rr = it;
				it++;
				s.erase(rr);
			}
		}
		/*for (int i = 1; i <= n; i++) {
			cout << ans[i] << " ";
		}
		cout << endl;*/
		return ans[n] >= k;
	};
	double l = 0.0, r = mx;
	while (r - l >= 1e-9) {
		double mid = (l + r) / 2;
		if (check(mid))
			l = mid;
		else
			r = mid;
	}
	cout << setprecision(8) << l << endl;
}
int main()
{
	ios::sync_with_stdio(false);
	cin.tie(nullptr);
	cout.tie(nullptr);
	int T = 1;
	while (T--)
		solve();
	return 0;
}