#include<bits/stdc++.h>
#define st first
#define nd second
#define pb push_back
#define eb emplace_back
#define pp pop_back
#define mp make_pair
#define all(x) (x).begin(), (x).end()
using namespace std;
using vi = vector<int>;
using pii = pair<int, int>;
using vii = vector<pii>;
using ll = long long;
using ld = long double;
mt19937 rng(chrono::high_resolution_clock::now().time_since_epoch().count());
int main(){
	int n;
	cin>>n;
	vector<ll> V(n+1);
	for(int i=1; i<=n; i++){
		cin>>V[i];
		V[i]+=V[i-1];
	}
	priority_queue<pair<ld, pii> > Q;
	ld ans=1e9;
	for(int i=1; i<=n; i++){
		Q.push(mp(-V[i]/ld(i), mp(1, i)));
	}
	ld m=V[n]/ld(n);
	while(true){
		auto t=Q.top();
		ans=min(ans, m+t.st);
		Q.pop();
		if(t.nd.nd==n)break;
		int l=t.nd.st, r=t.nd.nd;
		Q.push(mp((V[l-1]-V[r])/ld(r-l+1), mp(l+1, r+1)));
		m=max(m, (V[r]-V[l-1])/ld(r-l+1));
	}
	cout<<fixed<<setprecision(10)<<ans;
}