#include <bits/stdc++.h>
using namespace std;
using Graph = vector<vector<int>>;
const int INF = 1e9;
const int EPS = 1e-9;
int main() {
  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 ave = (v.at(0) + v.at(1)) / 2;
  double max = 0;
  for (int i = 2; i < N; ++i) {
    max = (ave + v.at(i)) / 2;
  }
  if (N == 2) max = ave;
  cout << max << endl;
}
