#include <bits/stdc++.h>
using namespace std;
int main() {
  long long N;
  cin >> N;
  vector<double> v(N);
  for (int i = 0; i < N; i++) cin >> v[i];
  priority_queue<double, vector<double>, greater<double>> PQ;
  for (int i = 0; i < N; i++) PQ.push(v[i]);
  double ans = 0;
  while (!PQ.empty()) {
    double t1 = PQ.top();
    PQ.pop();
    double t2 = PQ.top();
    PQ.pop();
    ans = (t1 + t2) / 2;
    PQ.push(ans);
  }
  cout << fixed << setprecision(10) << ans << endl;
}
