#include <bits/stdc++.h>
using namespace std;
int main() {
  int n;
  cin >> n;
  vector<int> vi(n);
  for (int &c : vi) {
    cin >> c;
  }
  sort(vi.begin(), vi.end());
  queue<int> visorted;
  for (int i = 0; i < n; i++) {
    visorted.push(vi.at(i));
  }
  int first = visorted.front();
  visorted.pop();
  int second = visorted.front();
  visorted.pop();
  double sum = (first + second) / 2;
  while (visorted.size() != 0) {
    sum = (sum + visorted.front()) / 2;
    visorted.pop();
  }
  cout << sum << endl;
}
