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