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