#include <bits/stdc++.h>
using namespace std;
int main() {
  int n;
  cin >> n;
  vector<double> v(n);
  for (int i = 0; i < n; i++) {
    cin >> v[i];
  }
  double max_v = 0;
  sort(v.begin(), v.end());
  do {
    double value = v[0];
    for (int i = 1; i < n; i++) {
      value = (value + v[i]) / 2.0;
    }
    max_v = max(max_v, value);
  } while (next_permutation(v.begin(), v.end()));
  printf("%.7f\n", max_v);
}
