#include <bits/stdc++.h>
using namespace std;
int main() {
  int n;
  cin >> n;
  vector<int> v(n);
  for (int i = 0; i < n; i++) {
    cin >> v[i];
  }
  double ans = 0;
  sort(v.begin(), v.end());
  do {
    for (int i = 0; i < n; i++) {
      double buf = v[i];
      for (int j = 0; j < n; j++) {
        if (i == j) {
          continue;
        }
        buf = (double)(buf + v[j]) / 2;
      }
      ans = max(ans, buf);
    }
  } while (next_permutation(v.begin(), v.end()));
  cout << ans << endl;
}
