#include <bits/stdc++.h>
using namespace std;
const int INF = 1e9;
const int MOD = 1000000007;
int main() {
  int N;
  cin >> N;
  vector<int> v(N);
  for (int i = (0); i < (N); i++) {
    cin >> v[i];
  }
  sort((v).begin(), (v).end());
  int div_num = 1;
  for (int i = (0); i < (N - 1); i++) {
    div_num *= 2;
  }
  double sum_v = ((double)v[0]) / div_num;
  for (int i = (1); i < (N); i++) {
    sum_v += ((double)v[i]) / div_num;
    div_num /= 2;
  }
  cout << sum_v << endl;
  return 0;
}
