#include <bits/stdc++.h>
using namespace std;
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  int n;
  cin >> n;
  long long A[n];
  for (int i = 0; i < n; ++i) cin >> A[i];
  sort(A, A + n);
  double ans = (double)A[0] / (1 << (n - 1));
  for (int i = 1; i < n; ++i) ans += (double)A[i] / (1 << (n - i));
  cout << setprecision(12) << ans << '\n';
}
