#include <bits/stdc++.h>
using namespace std;
int main() {
  int n;
  cin >> n;
  int h[n];
  for (int i = 0; i < n; i++) cin >> h[i];
  sort(h, h + n);
  double sin = (h[0] + h[1]) / 2;
  double g;
  for (int i = 2; i < n; i++) {
    sin = (sin + h[i]) / 2;
  }
  cout << sin;
  return 0;
}
