#include<bits/stdc++.h>
using namespace std;

int main(){
	int n;cin >> n;
  	vector<int> a;
  	while(n--){int x;cin >> x;a.push_back(x);}
  	sort(a.begin(),a.end());
  	int best = 0;
  	do{
      	int now = a[0];
    	for(auto i : a){now = (i+now)/2;}
      	best = max(best,now);
    }while(next_permutation(a.begin(),a.end());
	cout << fixed << setprecision(6) << best << "\n";
}