#include <bits/stdc++.h>
using namespace std;
int main() {
  int n;
  cin >> n;
  vector<float> v;
  for (int i = 0; i < n; i++) {
    float a;
    cin >> a;
    v.push_back(a);
  }
  while (v.size() != 1) {
    float min1 = *min_element(v.begin(), v.end());
    v.erase(std::remove(v.begin(), v.end(), min1), v.end());
    float min2 = *min_element(v.begin(), v.end());
    v.erase(std::remove(v.begin(), v.end(), min2), v.end());
    float moy = (min1 + min2) / 2.0;
    v.push_back(moy);
  }
  printf("%.5f", v[0]);
  return 0;
}
