#include <bits/stdc++.h>
using namespace std;
int main() {
  int n;
  cin >> n;
  vector<double> vi;
  for (int i = 0; i < n; i++) {
    double x;
    cin >> x;
    vi.push_back(x);
  }
  while (vi.size() > 1) {
    vector<double> tmp;
    sort(vi.begin(), vi.end(), greater<int>());
    for (int i = 1; i < vi.size(); i++) {
      tmp.push_back((vi[i] + vi[0]) / 2);
    }
    vi.clear();
    for (int i = 0; i < tmp.size(); i++) vi.push_back(tmp[i]);
  }
  cout << vi[0];
  return 0;
}
