#include using namespace std; typedef long long ll; int n; vectorv; ll k; bool ok(double mid) { ll ans = 0; for (int i = 0; i < n; i++) { ans += (v[i] / mid); } return (ans >= k); } int main() { // #ifndef ONLINE_JUDGE // freopen("input.txt", "r", stdin); // freopen("output.txt", "w", stdout); // #endif ios_base::sync_with_stdio(false); cin.tie(NULL); cin >> n; v.resize(n); for (int i = 0; i < n; i++) { cin >> v[i]; } cin >> k; double long left = 0, right = 1e9 + 1; for (int rep = 0; rep < 40; rep++) { double long mid = (left + right) / 2.0; if (ok(mid))left = mid; else right = mid; } cout << setprecision(9) << fixed << left << endl; }