#include <bits/stdc++.h>
using namespace std;
int main() {
  int N;
  cin >> N;
  vector<double> L(N);
  for (int i = 0; i < N; i++) {
    cin >> L[i];
  }
  sort(L.begin(), L.end());
  double t = L[0];
  for (int i = 0; i < N - 1; i++) {
    t = (t + L[i + 1]) / 2;
  }
  cout << t << endl;
}
