#include<bits/stdc++.h> 
using namespace std;
const int N=110000;
const double eps=1e-6;
double a[N],sum;
int n,k;
bool check(double x)
{
    double s=0;
    for(int i=2;i<n;i++)
    {
        if(s>0)s+=a[i];
        else   s=a[i];
        if(sum-s<=0)return 1;
    }
    return 0;
}
int main()
{
    scanf("%d",&n);
    double l=0,r=0,ans;
    for(int i=1;i<=n;i++)scanf("%lf",&a[i]),r+=a[i];
    sum=r;
    while(l<r)
    {
        double mid=(l+r)/2;
        for(int i=2;i<n;++i)a[i]-=mid;
        sum-=mid*n;
        if(check(mid))r=mid-eps,ans=mid;
        else          l=mid+eps;
        for(int i=2;i<n;++i)a[i]+=mid;
        sum+=mid*n;
    }
    printf("%.3lf",ans);
    return 0;
}