#include <bits/stdc++.h>
using namespace std;
int main() {
  int n;
  float new_ing, avg;
  cin >> n;
  float v[n];
  for (int i = 0; i < n; i++) {
    cin >> v[i];
  }
  sort(v, v + n);
  new_ing = (v[0] + v[1]) / 2;
  for (int i = 2; i < n; i++) {
    avg = (new_ing + v[i]) / 2;
    new_ing = avg;
  }
  cout << avg;
  return 0;
}
