#include <bits/stdc++.h>
using namespace std;
using ll = long long;
int main() {
  int n;
  vector<double> v(n);
  for (int i = 0; i < (n); ++i) cin >> v.at(i);
  sort(v.begin(), v.end());
  double ans = v.at(0);
  for (int i = 1; i < n; i++) {
    ans += v.at(i) * pow(2, i - 1);
  }
  ans /= pow(2, n - 1);
  cout << ans << endl;
  return 0;
}
