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