#include <bits/stdc++.h>
using namespace std;
int main() {
  int n;
  cin >> n;
  queue<double> r;
  vector<double> nex;
  double m = 0;
  for (int i = 0; i < n; i++) {
    cin >> m;
    nex.push_back(m);
  }
  sort(nex.begin(), nex.end());
  for (auto &x : nex) {
    r.push(x);
  }
  double sum = r.front();
  r.pop();
  while (r.size()) {
    double sec = r.front();
    r.pop();
    sum = (sum + sec) / 2;
  }
  cout << sum << endl;
  return 0;
}
