#include <bits/stdc++.h>
using namespace std;
void solve() {
  int n;
  cin >> n;
  vector<double> v;
  for (int i = 0; i < n; i++) {
    int x;
    cin >> x;
    v.push_back(x);
  }
  while (v.size() > 1) {
    sort(v.begin(), v.end());
    int a = v[0], b = v[1];
    v.erase(v.begin(), v.begin() + 2);
    v.push_back((a + b) / 2.0);
  }
  cout << fixed << setprecision(6) << v[0] << endl;
  return;
}
int main() {
  solve();
  return 0;
}
