#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];
  }
  while (v.size() != 1) {
    sort(v.begin(), v.end());
    v.push_back((v[0] + v[1]) / 2.0);
    v.erase(v.begin() + 0);
    v.erase(v.begin() + 0);
    n--;
  }
  cout << setprecision(16) << v[0] << endl;
}
