#include <bits/stdc++.h>
using namespace std;
int main() {
  int N;
  cin >> N;
  float V[N];
  for (int i = 0; i < (int)(N); i++) cin >> V[i];
  sort(V, V + N);
  float ans = V[0] / (1 << N);
  for (int i = 0; i < (int)(N); i++) ans += V[i] / (1 << (N - i));
  cout << ans << endl;
}
