#include <bits/stdc++.h>
using namespace std;
int main() {
  int a, n;
  set<int> s;
  set<int>::iterator it;
  cin >> n;
  if (n >= 2 && n <= 50) {
    while (n--) {
      cin >> a;
      if (a >= 1 && a <= 1000) s.insert(a);
    }
    double sum = 0;
    it = s.begin();
    sum = *it;
    it++;
    for (; it != s.end(); it++) {
      sum = (sum + *it) / 2;
    }
    cout << sum << endl;
  } else
    return 0;
}
