#include <iostream>

void Swap(float& a, float& b)
{
	float temp = a;
	a = b;
	b = temp;
	
}
void InsertSor(float src[],int n)
{
	
	for (int i = 1; i < n; ++i)
	{
		for (int j = i; j >= 1; --j)
		{
			Swap(src[i], src[j]);
		}
	}
}


int main()
{

	int N;
	std::cin >> N;
	float* ana;
	ana = new float[N];
	for (int i = 0; i < N; i++)
	{
		std::cin >> ana[i];
	}
	/*
	for (int i = 0; i < N-1; ++i)
	{
		InsertSor(ana, N - i );
		float new_gu = (ana[N-i-1] + ana[N-i-2]) / 2.0;
		ana[N-i-2] = new_gu;

	}
	std::cout << ana[0];
*/
	InsertSor(ana, N);
	double sum=ana[N-1]/pow(2,N-1);
	for (int i = N-2; i >-1;--i)
	{

		sum += ana[i]/(pow(2,i+1));
	}
	std::cout << sum;
	delete[] ana;
	return 0;
}