#include <bits/stdc++.h>
using namespace std;
int main() {
  int n, i, x, j;
  double v[50], o, temp;
  cin >> n;
  for (i = 0; i < n; i++) {
    cin >> v[i];
  }
  for (i = 0; i < n; i++)
    for (j = i; j < n; j++) {
      if (v[i] > v[j]) {
        temp = v[i];
        v[i] = v[j];
        v[j] = temp;
      }
    }
  x = 1;
  o = 0;
  o = v[0] + v[1];
  for (i = 2; i < n; i++) {
    x *= 2;
    o += v[i] * x;
  }
  x *= 2;
  o /= x;
  cout << o;
  return 0;
}
