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