#include <bits/stdc++.h>
using namespace std;
const long long MOD = 1e9 + 7;
const long long N = 1e5 + 10;
long long gcd(long long n, long long m) {
  if (n == 0)
    return m;
  else
    return gcd(m % n, n);
}
double a[N];
int32_t main() {
  ios_base::sync_with_stdio(false);
  cin.tie(0);
  long long n;
  cin >> n;
  priority_queue<double, vector<double>, greater<double> > pq;
  for (long long i = 1; i <= n; i++) {
    cin >> a[i];
    pq.push(a[i]);
  }
  while (pq.size() > 1) {
    long long k = pq.top();
    pq.pop();
    double k1 = pq.top();
    pq.pop();
    pq.push((k1 + k) / 2.0);
  }
  cout << fixed << setprecision(12) << pq.top() << endl;
}
