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