#include <bits/stdc++.h>
using namespace std;
int n;
double ans = 0;
double a[51];
int h[51];
double go() {
  double sum = a[h[0]];
  for (int i = 1; i < n; i++) sum = (sum + a[h[i]]) / 2;
  return sum;
}
int main() {
  cin >> n;
  for (int i = 0; i < n; i++) {
    h[i] = i;
    cin >> a[i];
  }
  do {
    ans = max(ans, go());
  } while (next_permutation(h, h + n));
  cout << ans << endl;
  return 0;
}
