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