#include <bits/stdc++.h>
using namespace std;
int main() {
  int N;
  vector<int> b;
  int a[100];
  cin >> N;
  for (int i = 0; i < N; i++) {
    cin >> a[i];
    b.push_back(a[i]);
  }
  sort(b.begin(), b.end());
  double res = ((double)b[0] + (double)b[1]) / 2;
  for (int k = 0; k < N - 2; k++) {
    res = (res + (double)b[k + 2]) / 2;
  }
  cout << res << endl;
}
