#include <bits/stdc++.h>
using namespace std;
const int N = 100005;
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  cout.tie(NULL);
  ;
  cout << fixed << setprecision(6);
  int n;
  cin >> n;
  vector<int> v(n);
  for (long long i = (long long)(0); i < (long long)(n); ++i) {
    cin >> v[i];
  }
  double ans = 0;
  if (v.size() % 2 == 0) {
    for (long long i = (long long)(0); i < (long long)(n); ++i) {
      ans += v[i];
    }
    ans /= v.size();
  } else {
    sort((v).begin(), (v).end());
    reverse((v).begin(), (v).end());
    ans += v.back();
    v.pop_back();
    ans += v.back();
    v.pop_back();
    ans /= 2;
    while (!v.empty()) {
      ans += v.back();
      v.pop_back();
      ans /= 2;
    }
  }
  cout << ans << "\n";
  ;
  cout << "\n";
  ;
  return 0;
}
