#include <bits/stdc++.h>
using namespace std;
int main() {
  int n, f = 0, b = 0, j = 0, c;
  cin >> n;
  vector<int> a(n);
  for (int i = 0; i < n; i++) {
    cin >> a[i];
  }
  while (1) {
    for (int i = 0; i < n - 1; i++) {
      if (a[i + 1] < a[i]) {
        swap(a[i], a[i + 1]);
        f = 1;
      }
    }
    if (f == 0) break;
    f = 0;
  }
  for (int i = 0; i < n; i++) {
    c = 2;
    j = 0;
    while (j < i - 1) {
      a[i] *= 2;
      c *= 2;
      j++;
    }
    b += a[i];
  }
  cout << (double)b / (double)c << endl;
}
