#include <bits/stdc++.h>
int main() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);
  cout.tie(0);
  ;
  int n;
  cin >> n;
  int a[n];
  cin >> a[0];
  long double sum = a[0];
  for (int i = 1; i < n; i++) {
    cin >> a[i];
    sum = (sum + a[i]) / 2.0;
  }
  cout << sum;
}
