#include <bits/stdc++.h>
using namespace std;
long long gcd(long long a, long long b) {
  if (!b) return a;
  return gcd(b, a % b);
}
long long lcm(long long a, long long b) { return a * b / gcd(a, b); }
signed main() {
  long long n;
  cin >> n;
  long long a[n];
  for (long long i = 0; i < n; i++) cin >> a[i];
  sort(a, a + n);
  double ans = (double)(a[0] + a[1]) / 2;
  for (long long i = 2; i < n; i++) {
    ans = (double)(ans + a[2]) / 2;
  }
  cout << ans << endl;
  return 0;
}
