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