#include <bits/stdc++.h>
using namespace std;
int main() {
  int N;
  cin >> N;
  vector<int> v(N);
  for (int i = 0; i < N; i++) {
    v.at(i);
  }
  double ANS = 0;
  stable_sort(v.begin(), v.end());
  ANS = (v.at(0) + v.at(1)) / 2;
  for (int i = 2; i < N; i++) {
    ANS = (ANS + v.at(i)) / 2;
  }
  cout << ANS << endl;
}
