#include <bits/stdc++.h>
using namespace std;
multiset<double> s;
int main() {
  int n;
  cin >> n;
  double x;
  for (int i = 0; i < n; i++) {
    cin >> x;
    s.insert(x);
  }
  while (s.size() > 1) {
    set<double>::iterator it = s.begin();
    double u = *it;
    s.erase(u);
    it = s.begin();
    double v = *it;
    s.erase(v);
    s.insert((u + v) / 2);
  }
  printf("%.6lf\n", *s.begin());
  return 0;
}
