#include <bits/stdc++.h>

using namespace std;

int main() {
	int n; cin >> n;
  	vector <int> a(n);
  for(int i = 0; i < n; i+=1) {
    cin >> a[i];
  }
  sort(a.begin(), a.end());
  double res = a[0];
  for(int i = 1; i < a.size(); i+= 1) {
  	res = (a[i] + prev)/2;
  }
  cout << res << endl;
}
