#include <bits/stdc++.h>
using namespace std;
int main() {
  int n;
  cin >> n;
  double res;
  cin >> res;
  double a;
  for (int i = 1; i < n; i++) {
    cin >> a;
    res = (res + a) / 2;
  }
  cout << res;
  return 0;
}
