#include <bits/stdc++.h>
using namespace std;
int main() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);
  long long int n;
  cin >> n;
  vector<long long int> v(n);
  for (long long int i = 0; i < n; i++) {
    cin >> v[i];
  }
  sort(v.begin(), v.end());
  double sum = (v[0] + v[1]) / 2;
  for (long long int i = 1; i < n - 1; i++) {
    sum = (sum + v[i + 1]) / 2;
  }
  cout << sum;
  return 0;
}
