#include <bits/stdc++.h>
using namespace std;
int main() {
  int n;
  cin >> n;
  vector<float> v(n);
  for (float &i : v) cin >> i;
  sort(v.begin(), v.end());
  n--;
  while (n--) {
    float k = v[v.size() - 1] + v[v.size() - 2];
    k /= 2.0;
    v.pop_back();
    v.pop_back();
    v.push_back(k);
    sort(v.begin(), v.end());
  }
  cout << v.back() << "\n";
  return 0;
}
