#include <bits/stdc++.h>
using namespace std;
int main(void) {
  int N;
  cin >> N;
  vector<double> v(N);
  for (int i = 0; i < N; i++) {
    cin >> v[i];
  }
  sort(v.begin(), v.end());
  for (int i = 0; i < N - 1; i++) {
    double new_v = (v[0] + v[1]) / 2;
    v.push_back(new_v);
    v.erase(v.begin(), v.begin() + 2);
  }
  cout << fixed << setprecision(5) << v[0] << endl;
  return 0;
}
