#include <bits/stdc++.h>
using namespace std;
const int N = int(2e5) + 2;
const int LG = 20;
const long long mod = (int)1e9 + 7;
const int INF = (int)1e9 + 7;
const long long linf = 1e18;
const long double pi = acos(-1);
const int base = 10;
const long double EPS = 1e-9;
int n;
set<long double> st;
int main() {
  cin >> n;
  for (int i = 1; i <= n; ++i) {
    long double x;
    cin >> x;
    st.insert(x);
  }
  while (((int)(st).size()) > 1) {
    long double a = *st.begin();
    auto to = st.end();
    to--;
    long double b = *to;
    st.erase(to);
    st.erase(st.begin());
    long double cur = (a + b) / 2.0;
    st.insert(cur);
  }
  long double ans = *st.begin();
  cout << fixed << setprecision(9) << ans << "\n";
}
