#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.at(i);
  }
  sort(v.begin(), v.end(), greater<float>());
  for (int i = N; i >= 2; i--) {
    int x;
    x = (v.at(i - 2) + v.at(i - 1)) / 2.0;
    v.pop_back();
    v.pop_back();
    v.push_back(x);
  }
  cout << v.at(0) << endl;
}
