#include <bits/stdc++.h>
using namespace std;
int main(int argc, const char* argv[]) {
  int N;
  cin >> N;
  vector<double> v(N);
  for (int i = 0; i < N; i++) {
    cin >> v.at(i);
  }
  sort(v.begin(), v.end());
  double ans = (v.at(0) + v.at(1)) / 2.0;
  for (int i = 2; i < N; i++) {
    ans = (v.at(i) + ans) / 2.0;
  }
  cout << ans << endl;
  return 0;
}
