#include <bits/stdc++.h>
using namespace std;
signed main() {
  long long n;
  cin >> n;
  priority_queue<long double> pq;
  while (n--) {
    long double x;
    cin >> x;
    pq.push(x);
  }
  while (!pq.empty()) {
    long double x = pq.top();
    pq.pop();
    if (pq.empty()) {
      cout << x << "\n";
      break;
    }
    long double y = pq.top();
    pq.pop();
    pq.push((x + y) / (long double)2);
  }
  return 0;
}
