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