#include <bits/stdc++.h>
using namespace std;
int main() {
  int N;
  cin >> N;
  vector<double> A(100000);
  for (int i = 0; i < N; i++) {
    cin >> A[i];
  }
  sort(A.begin(), A.end());
  for (int i = 0; i < N - 1; i++) {
    A[i + 1] = (A[i] + A[i + 1]) / 2;
  }
  cout << A[N - 1] << endl;
}
