import java.util.Scanner;

public class Main {

	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int N = sc.nextInt();
		double[] A = new double[N];
		double tmp;
		double ans = 0;
		for(int i=0;i<N;i++) {
			A[i] = sc.nextDouble();
 		}
		for(int i=0;i<N;i++) {
			for(int j=i+1;j<N;j++) {
				if(A[i] > A[j]) {
					tmp = A[i];
					A[i] = A[j];
					A[j] = tmp;
				}
			}
		}
		for(int i=0;i<N;i++) {
			ans += A[i]/Math.pow(2,N-i);
			if(i == 0) {
				ans += A[i]/Math.pow(2,N-i);
			}
		}
		System.out.println(ans);
	}
}
/tmp/hf-datasets-cache/medium/datasets/42704881117311-config-parquet-and-info-qiankunmu-Project_CodeNet-896c9d36/hub/datasets--qiankunmu--Project_CodeNet_Python800_and_Java250/snapshots/c899fde44a77ba1cc14973ed3de064e4ff3aadc7/Project_CodeNet_Java250.tar.gz