#include <iostream>
#include <algorithm>
#include <iomanip>
#include <vector>

using namespace std;

int main(){
  int n;
  cin >> n;
  vector <double> a(n);
  for (int i = 0; i < n; i++) cin >> a[i];
  double avg = a[0];
  for (int i = 1; i < n; i++){
    avg = (avg + a[i])/2;
  }
  cout << setprecision(7) << setiosfalgs(ios::fixed) << setiosflags(ios::showpoint) << avg;
}