#include <bits/stdc++.h>
using namespace std;
#define double long double
const int N = 2'000 + 10;
const double MAX = 1e9;
int n;
int a[N];
long long pref[N];
inline long long sum(int l, int r) { return pref[r] - pref[l - 1]; }
inline double cal(int l, int r) { return (double)sum(l, r) / (r - l + 1); }
int way[N][N];
double f[N][N];
pair<int, int> par[N][N];
bool mk[N][N];
int32_t main() {
cin.tie(0)->sync_with_stdio(0);
cin >> n;
for (int i = 1; i <= n; ++i) cin >> a[i];
for (int i = 1; i <= n; ++i) pref[i] = pref[i - 1] + a[i];
for (int i = 1; i <= n; ++i) {
for (int j = 1; j <= n; ++j) f[i][j] = MAX;
}
f[1][n] = cal(1, n);
using TP = tuple<double, int, int>;
priority_queue<TP, vector<TP>, greater<>> q;
double answer = MAX;
auto go = [&](int x, int y) {
if (!x && !y) return;
double mi = MAX;
while (x != y) {
f[x][y] = max(f[x][y], cal(x, y));
if (!mk[x][y]) q.emplace(cal(x, y), x, y), mk[x][y] = true;
mi = min(mi, cal(x, y));
int nX = (!way[x][y] ? x : x + 1), nY = (!way[x][y] ? y - 1 : y);
f[nX][nY] = f[x][y];
par[nX][nY] = {x, y};
tie(x, y) = {nX, nY};
}
f[x][y] = max(f[x][y], cal(x, y));
if (!mk[x][y]) q.emplace(cal(x, y), x, y), mk[x][y] = true;
mi = min(mi, cal(x, y));
answer = min(answer, f[x][y] - min(cal(1, n), get<0>(q.top())));
};
go(1, n);
while (q.size()) {
auto [d, i, j] = q.top(); q.pop();
auto [x, y] = par[i][j];
if (way[x][y]) continue;
way[x][y] = 1;
go(x, y);
}
cout << setprecision(9) << fixed << answer << "\n";
}
