#include <bits/stdc++.h>
using namespace std;
int main() {
  int n;
  cin >> n;
  vector<double> v(n);
  for (int i = 0; i < n; ++i) cin >> v[i];
  sort(v.begin(), v.end());
  double ans = 0, res;
  ans = (v[0] + v[1]) / 2;
  for (int i = 2; i < n; ++i) {
    res = (ans + v[i]) / 2;
  }
  if (n == 2) {
    cout << ans;
    return 0;
  }
  cout << fixed << setprecision(10) << res;
  return 0;
}
