#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using P = pair<int, int>;
const int INF = 1001001001;
int main() {
  int n;
  cin >> n;
  vector<double> v(n);
  for (int i = 0; i < (n); ++i) cin >> v[i];
  sort(v.begin(), v.end());
  double ans = (v[0] + v[1]) / pow(2, (n - 1));
  for (int i = 2; i < n; i++) {
    ans += v[i] / pow(2, (i - 1));
  }
  printf("%.8f", ans);
  return 0;
}
