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

double v[50];

int main(void){
  int n; cin >> n;
  for(int i = 0;i < n;i++)cin >> v[i];
  sort(v, v + n);
  double ave = v[0];
  for(int i = 1;i < n;i++)ave = (ave + v[i])/2.0;
  cout << ave << endl;
}