#include <bits/stdc++.h>
using namespace std;
int main() {
  int n;
  cin >> n;
  vector<float> v;
  v.reserve(n);
  for (int i = 0; i < n; i++) {
    float tmp = 0;
    cin >> tmp;
    v.push_back(tmp);
  }
  sort(v.begin(), v.end());
  float tmp = 0.0;
  for (int i = 0; i < n - 1; i++) {
    tmp = (v[0] + v[1]) / 2;
    v.push_back(tmp);
    v.erase(v.begin());
    v.erase(v.begin() + 1);
    sort(v.begin(), v.end());
  }
  cout << v[1] << endl;
  return 0;
}
