#include <bits/stdc++.h>
using namespace std;
int n;
double x;
vector<double> a, b;
int main() {
  ios::sync_with_stdio(false);
  cin.tie(0);
  cin >> n;
  for (int i = 0; i < n; i++) {
    cin >> x;
    a.push_back(x);
  }
  sort(a.begin(), a.end());
  while (1) {
    for (int i = 0; i < a.size(); i += 2) {
      if (i + 1 >= n)
        b.push_back(a[i]);
      else
        b.push_back((double)(a[i] + a[i + 1]) * 0.5);
    }
    a.clear();
    a = b;
    b.clear();
    if (a.size() == 1) break;
  }
  cout << a[0];
  return 0;
}
