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