#include <bits/stdc++.h>
using namespace std;
void solve() {
  int n;
  cin >> n;
  vector<double> v(n);
  for (int i = 0; i < n; i++) {
    cin >> v[i];
  }
  sort(v.begin(), v.end());
  double maxval = 0;
  double current = 0;
  do {
    current = v[0];
    for (int i = 1; i < n; i++) {
      current = (current + v[i]) / 2;
    }
    maxval = max(maxval, current);
  } while (next_permutation(v.begin(), v.end()));
  cout << maxval << endl;
}
int main() {
  solve();
  return 0;
}
