#include <bits/stdc++.h>
using namespace std;
int main() {
  int n;
  int a[55];
  vector<int> v;
  int v1;
  double max = 0;
  cin >> n;
  for (int i = 1; i <= n; i++) {
    cin >> a[i];
  }
  for (int i = 1; i <= n; i++) {
    v.push_back(i);
  }
  do {
    double sum = a[v[0]];
    for (int i = 1; i < n; i++) {
      sum += a[v[i]];
      sum /= 2;
      if (i == n - 1) {
        if (max < sum) max = sum;
      }
    }
  } while (next_permutation(v.begin(), v.end()));
  printf("%.10f", max);
}
