#include <bits/stdc++.h>
using ll = long long;
int M = 100100100;
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 = (v[0] + v[1]) / 2;
  if (n == 2) {
    cout << ans;
    return 0;
  }
  for (int i = 2; i < n; i++) {
    ans = (ans + v[i]) / 2;
    v.push_back(ans);
    sort(v.begin(), v.end());
  }
  cout << ans;
}
