#include <bits/stdc++.h>
using namespace std;
int main() {
  int N;
  cin >> N;
  vector<int> v(N);
  for (int i = 0; i < N; i++) {
    cin >> v[i];
  }
  sort(v.begin(), v.end());
  if (v.size() == 2) {
    cout << (long double)accumulate(v.begin(), v.end(), 0) / v.size() << endl;
    return 0;
  } else {
    for (int i = 2; i < N; i++) {
      v[i] = pow(2.0, i - 1) * v[i];
    }
    cout << (long double)accumulate(v.begin(), v.end(), 0) /
                pow(2.0, v.size() - 1)
         << endl;
    return 0;
  }
}
