#include <bits/stdc++.h>
using namespace std;
int dx[4] = {1, 0, -1, 0}, dy[4] = {0, 1, 0, -1};
const int MOD = 1000000007;
int main() {
  cin.tie(0);
  ios::sync_with_stdio(false);
  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 in = (v[0] + v[1]) / 2;
  double temp;
  for (int i = 2; i < n; i++) {
    temp = (v[i] + in) / 2;
    in = temp;
  }
  cout << temp << '\n';
}
