#include <bits/stdc++.h>
using namespace std;
int power(int a, int b) {
  int res = 1;
  while (b > 0) {
    if (b & 1) res = res * a;
    a = a * a;
    b >>= 1;
  }
  return res;
}
int main() {
  int n;
  cin >> n;
  int count = 0;
  vector<double> v(n);
  for (int i = 0; i < n; i++) {
    cin >> v[i];
    if (i > 0 && (v[i] == v[i - 1])) count += 1;
  }
  if (count == (n - 1))
    cout << v[0] << "\n";
  else {
    sort(v.begin(), v.end());
    double sum = 0;
    double min1 = v[0];
    double min2 = v[1];
    int p = n - 2;
    sum = (min1 / (power(2, n - 1)) + min2 / (power(2, n - 1)));
    for (int i = 2; i < n; i++) {
      sum += v[i] / (power(2, p++));
    }
    cout << sum << "\n";
  }
  return 0;
}
