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