#include <bits/stdc++.h>
using namespace std;
const bool DEBUG = true;
using ll = long long;
using ii = pair<int, int>;
using vi = vector<int>;
const double PI = acos(-1);
const double EPS = 1e-9;
int main() {
  ios::sync_with_stdio(0);
  cout << fixed << setprecision(10);
  int n;
  cin >> n;
  set<double> st;
  for (int i = 0; i < n; ++i) {
    int x;
    cin >> x;
    st.insert(x);
  }
  while (int(st.size()) > 1) {
    auto it = st.begin();
    int a = *it;
    st.erase(it);
    it = st.begin();
    int b = *it;
    st.erase(it);
    st.insert(((a + b) / 2.0));
  }
  cout << *st.begin() << endl;
}
