#include <bits/stdc++.h>
using namespace std;
int main() {
  int n, t;
  float ans;
  vector<int> a;
  cin >> n;
  for (int i = 0; i < n; i++) {
    cin >> t;
    a.push_back(t);
  }
  sort(a.begin(), a.end());
  if (n == 2)
    ans = (float)(a[0] + a[1]) / 2;
  else {
    ans = (a[0] + a[1]) / 2;
    for (int i = 2; i < n; i++) {
      ans = (float)(ans + a[i]) / 2;
    }
  }
  printf("%.5f\n", ans);
  return 0;
}
