#include <bits/stdc++.h>
using namespace std;
const bool DEBUG = false;
int main(int argc, char const *argv[]) {
  int N;
  cin >> N;
  double tmp;
  set<double> v;
  for (size_t i = 0; i < N; i++) {
    cin >> tmp;
    v.insert(tmp);
  }
  bool first = true;
  double total;
  for (auto itr = v.begin(); itr != v.end(); itr++) {
    if (first) {
      total = *itr;
      first = false;
      continue;
    }
    total = (total + *itr) / 2;
  }
  cout << total << endl;
  return 0;
}
