#include <bits/stdc++.h>
using namespace std;
int main() {
  int n = 0;
  cin >> n;
  vector<int> vi(n);
  for (int &c : vi) {
    cin >> c;
  }
  sort(vi.begin(), vi.end());
  vector<double> sum(n - 1, 0);
  for (int i = 0; i < n - 1; i++) {
    if (i == 0) {
      sum.at(0) = (vi.at(0) + vi.at(1)) / 2;
    } else {
      sum.at(i) = (sum.at(i - 1) + vi.at(i + 1)) / 2;
    }
  }
  cout << sum.at(n - 2) << endl;
}
