#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;
const int MAXN = 2e5;
int N, A[MAXN+10];
ll S[MAXN+10];
bool cmp(pii p, pii q)
{
p.first--; q.first--;
return (__int128)(S[p.second]-S[p.first])*(q.second-q.first) < (__int128)(S[q.second]-S[q.first])*(p.second-p.first);
}
pii mmin(pii p, pii q)
{
if(cmp(p, q)) return p;
else return q;
}
pii mmax(pii p, pii q)
{
if(cmp(p, q)) return q;
return p;
}
pii B[MAXN+10], C[MAXN+10];
int T[MAXN+10];
double ans=1e18;
double avg(pii x)
{
x.first--;
return (double)(S[x.second]-S[x.first])/(x.second-x.first);
}
void f(pii l, pii r)
{
//printf("%d %d / %d %d\n", l.first, l.second, r.first, r.second);
ans=min(ans, avg(r)-avg(l));
}
struct CMP
{
bool operator () (const pair<pii, int> &p, const pair<pii, int> &q) const
{
return !cmp(p.first, q.first);
}
};
int main()
{
scanf("%d", &N);
for(int i=1; i<=N; i++) scanf("%d", &A[i]), S[i]=S[i-1]+A[i];
for(int i=1; i<=N; i++)
{
int lo=0, hi=N-i+2;
while(lo+1<hi)
{
int mid=lo+hi>>1;
if(cmp(pii(mid, mid+i-1), pii(1, N))) lo=mid;
else hi=mid;
}
B[i]=pii(lo, lo+i-1);
C[i]=pii(hi, hi+i-1);
}
pii l(1, N), r(1, N);
priority_queue<pair<pii, int>, vector<pair<pii, int>>, CMP> PQ;
for(int i=1; i<=N; i++)
{
if(1<=B[i].first && C[i].second<=N) PQ.push({B[i], i}), r=mmax(r, B[i]);
else if(1<=B[i].first) l=mmin(l, B[i]), r=mmax(r, B[i]);
else l=mmin(l, C[i]), r=mmax(r, C[i]);
}
while(!PQ.empty())
{
auto t=PQ.top(); PQ.pop();
f(mmin(l, t.first), r);
//printf("WOW %d %d\n", t.first.first, t.first.second);
r=mmax(r, C[t.second]);
l=mmin(l, C[t.second]);
}
f(l, r);
printf("%.10lf\n", ans);
}
