#include <bits/stdc++.h>
using namespace std;
int gcd(long long a, long long b) {
  long long M = max(a, b), m = min(a, b);
  while (m != 0) {
    long long r = M % m;
    M = m;
    m = r;
  }
  return M;
}
int digit_sum(long long n) {
  long long ans;
  while (n != 0) {
    ans += n % 10;
    n /= 10;
  }
  return ans;
}
int main() {
  int n;
  cin >> n;
  vector<int> a(n);
  for (int i = 0; i < n; i++) {
    cin >> a.at(i);
  }
  sort(a.begin(), a.end());
  double ans = (a.at(0) + a.at(1)) / 2;
  for (int i = 2; i < n; i++) {
    ans = (ans + a.at(i)) / 2;
  }
  cout << fixed << setprecision(10);
  cout << ans << endl;
}
