#include <bits/stdc++.h>
using namespace std;
int main() {
  int n;
  cin >> n;
  vector<float> v(n);
  for (int i = 0; i < n; i++) {
    cin >> v[i];
  }
  while (1 < v.size()) {
    sort(v.begin(), v.end());
    v.push_back((v[0] + v[1]) / 2);
    v.erase(v.begin(), v.begin() + 2);
    v.shrink_to_fit();
  }
  cout << v[0] << endl;
  return 0;
}
