#include <bits/stdc++.h>
using namespace std;
long double v[1000];
int main() {
  int n;
  cin >> n;
  long double ans = 0, val;
  for (int i = 0; i < n; ++i) {
    cin >> v[i];
  }
  sort(v, v + n);
  do {
    val = v[0];
    for (int i = 1; i < n; ++i) {
      val = (val + v[i]) / 2;
    }
    ans = max(ans, val);
  } while (next_permutation(v, v + n));
  cout << ans << '\n';
  return 0;
}
