#define ll long long
#define MOD 1000000007 
#define mp make_pair
#define pb push_back
#define ff first
#define ss second
#define T long long t;cin>>t;while(t--)
#define foe(i) for(int i=1;i<=n;i++)
#define fo(i) for(int i=0;i<n;i++)
#include <bits/stdc++.h>
using namespace std;
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  cout.tie(NULL);
  ll n;
  cin>>n;
  ll a[55];
  for(int i=0;i<n;i++)
  cin>>a[i];
  sort(a,a+n);
  a[1]+=a[0];
  long double ans=0;
  int j=1;
  for(int i=1;i<=pow(2,n-2);i=i*2)
  {
    ans+=i*a[j];
    j++;
  }
  ans=ans/pow(2,n-1);
  cout<<ans;
}