#include <bits/stdc++.h>
using namespace std;
int main() {
  int a, n;
  set<int> s;
  set<int>::iterator it;
  double d, sum = 0;
  cin >> a;
  while (a--) {
    cin >> n;
    s.insert(n);
  }
  it = s.begin();
  sum = *it;
  it++;
  sum += *it;
  it++;
  sum /= 2;
  for (; it != s.end(); it++) {
    sum = (sum + *it) / 2;
  }
  cout << sum << endl;
}
