#include <bits/stdc++.h>
using namespace std;
int main() {
  long long n;
  long double sum = 0.0, x, y;
  cin >> n;
  vector<long long> das;
  for (long long i = long long(0); i <= long long(n); i++) {
    cin >> x;
    das.push_back(x);
  }
  sort(das.begin(), das.end());
  x = (das[0] + das[1]) / 2.0;
  for (long long i = long long(2); i <= long long(n - 1); i++) {
    x = (x + das[i]) / 2.0;
  }
  cout << x << endl;
  return 0;
}
