import java.util.ArrayList;
import java.util.Collections;
import java.util.Scanner;

public class Stats {
    public static double calculateAverage(ArrayList<Double> numbers) {
        double total = 0;
        for (double num : numbers) {
            total += num;
        }

        return total / numbers.size();
    }

    public static double calculateMedian(ArrayList<Double> numbers) {
        // sort the list
        Collections.sort(numbers);

        if (numbers.size() % 2 == 0) {
            // take average of two middle numbers
            int middle1 = numbers.size() / 2;
            int middle2 = middle1 - 1;

            return (numbers.get(middle1) + numbers.get(middle2)) / 2;
        } else {
            // take the one middle number
            int middle = numbers.size() / 2;
            return numbers.get(middle);
        } 
    }

    public static void main(String args[]) {
        ArrayList<Double> numbers = new ArrayList<>();

        Scanner in = new Scanner(System.in);
        System.out.println("Enter some numbers (0 to stop).");

        double num = in.nextDouble();
        while (num != 0) {
            numbers.add(num);
            num = in.nextDouble();
        }
        
        double median = calculateMedian(numbers);
        System.out.println(median);
    }
}