#include <bits/stdc++.h>
using namespace std;
int main() {
  vector<double> v;
  int n;
  cin >> n;
  for (int i = 0; i < n; i++) {
    double a;
    cin >> a;
    v.push_back(a);
  }
  sort(v.begin(), v.end());
  reverse(v.begin(), v.end());
  double d = v[0];
  bool f = 0;
  if (n % 2 == 1) {
    f = 1;
    v.erase(v.begin());
  }
  double ans;
  while (v.size() > 1) {
    for (int i = 0; i < v.size(); i += 2) {
      v[i] = (v[i] + v[i + 1]) / 2;
      v[i + 1] = -1;
    }
    for (int i = 0; i < v.size(); i++) {
      if (v[i] == -1) v.erase(v.begin() + i);
    }
  }
  ans = v[0];
  if (f) ans = (ans + d) / 2;
  printf("%.10lf", ans);
  return 0;
}
