#include <bits/stdc++.h>
using namespace std;
using ll = long long;
int main() {
  int n;
  cin >> n;
  std::vector<double> vec(n);
  for (int i = 0; i < (int)n; ++i) cin >> vec.at(i);
  for (int i = 0; i < (int)n; ++i) {
    sort(vec.begin(), vec.end());
    double tmp = (vec.at(i) + vec.at(i + 1)) / 2.0;
    vec.at(i) = -1;
    vec.at(i + 1) = -1;
    vec.push_back(tmp);
    i++;
  }
  cout << vec.at(vec.size() - 1) << endl;
}
