#include <bits/stdc++.h>
using namespace std;
struct edge {
  int to;
  int weight;
  edge(int t, int w) : to(t), weight(w) {}
};
using Graph = vector<vector<int>>;
using dou = long double;
string Yes = "Yes";
string YES = "YES";
string NO = "NO";
string No = "No";
template <class T>
inline bool chmax(T& a, T b) {
  if (a < b) {
    a = b;
    return true;
  }
  return false;
}
template <class T>
inline bool chmin(T& a, T b) {
  if (a > b) {
    a = b;
    return true;
  }
  return false;
}
const int INF = 2000000000;
const long long INF64 = 922337203685477580ll;
const int mod = 1000000007ll;
const long long MOD = 1000000007LL;
const double pi = 3.1415926535897932384626;
int main() {
  int n;
  std::cin >> n;
  std::vector<double> a(n);
  for (int i = 0; i < (int)(n); i++) std::cin >> a[i];
  ;
  sort((a).begin(), (a).end());
  int ans = (a[0] + a[1]) / 2;
  for (int i = 1; i < (int)(n - 1); i++) {
    ans = (ans + a[i + 1]) / 2;
  }
  std::cout << fixed << setprecision(10) << ans << std::endl;
}
