#include <bits/stdc++.h>
using namespace std;
int main() {
  int N;
  double A[50];
  cin >> N;
  for (int i = 0; i < N; i++) cin >> A[i];
  sort(A, A + N);
  double ans = (A[0] + A[1]) / 2.0;
  for (int i = 2; i < N; i++) {
    ans = (ans + A[2]) / 2.0;
  }
  cout << setprecision(10) << ans << endl;
  return 0;
}
