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