#include <bits/stdc++.h>
#pragma GCC optimize("Ofast")
#pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,avx,tune=native")
using namespace std;
int main() {
  cin.tie(0);
  ios::sync_with_stdio(false);
  int N;
  cin >> N;
  vector<double> v(N);
  for (int i = 0; i < (int)(N); i++) cin >> v[i];
  sort(v.begin(), v.end());
  reverse(v.begin(), v.end());
  double p;
  for (int i = 0; i < (int)(N); i++) {
    p = (v[0] + v[1]) / 2;
    reverse(v.begin(), v.end());
    v.pop_back();
    v.pop_back();
    v.push_back(p);
    sort(v.begin(), v.end());
    reverse(v.begin(), v.end());
  }
  cout << v[0] << endl;
  return 0;
}
