#include <bits/stdc++.h>
using namespace std;
int n, a[55];
int main() {
  cin >> n;
  for (int i = (1); i <= n; ++i) cin >> a[i];
  sort(a + 1, a + 1 + n);
  double res = 0;
  for (int i = (2); i <= n; ++i) a[i] = (a[i - 1] + a[i]) / 2;
  cout << res;
}
