#include <bits/stdc++.h>
using namespace std;
int n, a[105];
int main() {
  ios::sync_with_stdio(0);
  cin.tie(0);
  cout.tie(0);
  cin >> n;
  for (int i = 1; i <= n; ++i) cin >> a[i];
  priority_queue<double> pq;
  for (int i = 1; i <= n; ++i) pq.push(a[i]);
  while (pq.size() > 1) {
    auto L = pq.top();
    pq.pop();
    auto R = pq.top();
    pq.pop();
    pq.push((L + R) / 2.0);
  }
  cout << fixed << setprecision(5) << pq.top();
  return 0;
}
