#include <bits/stdc++.h>
using namespace std;
const long long mod = 1e9 + 7;
using ll = long long;
using pii = pair<int, int>;
using pll = pair<ll, ll>;
unsigned long long gcd(unsigned long long a, unsigned long long b) {
  return b ? gcd(b, a % b) : a;
}
unsigned long long lcm(unsigned long long a, unsigned long long b) {
  return a / gcd(a, b) * b;
}
int main() {
  ios::sync_with_stdio(false);
  cin.tie(0);
  cout << fixed << setprecision(10);
  int n, temp;
  cin >> n;
  set<double> v{};
  for (int i = 0, i_len = (n); i < i_len; i++) {
    cin >> temp;
    v.insert(temp);
  }
  while (v.size() > 1) {
    auto itr = v.begin();
    double temp1 = *itr++;
    double temp2 = *itr;
    double temp3 = (temp1 + temp2) / 2;
    v.insert(temp3);
    v.erase(temp1);
    v.erase(temp2);
    v.insert(temp3);
  }
  auto itr = v.begin();
  cout << *itr << endl;
  return 0;
}
