int main()
{
	int N;
	cin >> N;
	
	vector<int> v(N);
	for (int i = 0; i < N; i++) {
		cin >> v[i];
	}

	sort(v.begin(), v.end());
	reverse(v.begin(), v.end());

	double mul = 1;
	double val = 0;
	for (int i = 0; i < N; i++) {
		if (i != N - 1)	mul *= 2;
		val += (v[i] / mul);
	}

	cout << val;
	return 0;
}

