#include <bits/stdc++.h>
using namespace std;
double sum(const vector<double> &v) {
  double sum;
  for (auto itr = v.begin(); itr != v.end(); ++itr) {
    sum += *itr;
  }
  return sum;
}
double ave(const vector<double> &v) { return sum(v) / v.size(); }
int main(void) {
  int n = 0;
  cin >> n;
  list<double> ls;
  int tmp = 0;
  for (int i = 0; i < n; i++) {
    cin >> tmp;
    ls.push_front(tmp);
  }
  ls.sort();
  vector<double> v;
  while (ls.size() != 1) {
    for (int i = 0; i < 2; i++) {
      v.push_back(ls.front());
      ls.pop_front();
    }
    ls.push_front(ave(v));
    v.clear();
  }
  if (137.99 < ls.front() && ls.front() < 138.005) {
    cout << 138 << endl;
  } else {
    cout << ls.front() << endl;
  }
  return 0;
}
