#include <bits/stdc++.h>
using namespace std;
const long long MOD = 1000000007;
const long long INF = 1e18;
const long long dx4[4] = {1, 0, -1, 0};
const long long dy4[4] = {0, 1, 0, -1};
const long long dx8[8] = {1, 1, 0, -1, -1, -1, 0, 1};
const long long dy8[8] = {0, 1, 1, 1, 0, -1, -1, -1};
const double pi = acos(-1);
template <class T>
inline bool chmin(T& a, T b) {
  if (a > b) {
    a = b;
    return true;
  }
  return false;
}
template <class T>
inline bool chmax(T& a, T b) {
  if (a < b) {
    a = b;
    return true;
  }
  return false;
}
using Graph = vector<vector<long long>>;
void solve() {
  std::ifstream in("sample.txt");
  std::cin.rdbuf(in.rdbuf());
  cin.tie(0);
  ios::sync_with_stdio(false);
  long long n;
  cin >> n;
  vector<long long> v(n);
  for (size_t i = (0); i < (n); ++i) cin >> v[i];
  sort((v).begin(), (v).end());
  double ans = 0;
  for (long long i = 0; i < n - 1; i++) {
    if (i == 0) {
      ans = (v[i] + v[i + 1]) / 2;
    } else {
      ans = (ans + v[i + 1]) / 2;
    }
  }
  cout << setprecision(10) << ans << endl;
}
signed main() {
  solve();
  return 0;
}
