#include <bits/stdc++.h>
using namespace std;
int main(void) {
  int n = 0;
  cin >> n;
  list<double> ls;
  double tmp = 0;
  for (int i = 0; i < n; i++) {
    cin >> tmp;
    ls.push_front(tmp);
  }
  ls.sort();
  while (ls.size() != 1) {
    tmp = ls.front();
    ls.pop_front();
    tmp += ls.front();
    ls.pop_front();
    ls.push_front(tmp / 2);
  }
  cout << ls.front() << endl;
  return 0;
}
