import java.util.*;

class Main {
    public static void main(String[] args) {

        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        List<Integer> list = new ArrayList<>();
        for (int i = 0; i < n; i++) {
            list.add(sc.nextInt());
        }
        list.sort(Comparator.naturalOrder());
        int half = n/2-1;
        int result = 0;
        if (list.get(half).equals(list.get(half+1))) {
            System.out.println(result);
            return;
        }
        result = list.get(half+1) - list.get(half);
        System.out.println(result);
    }
} import java.util.*; util.* java class Main {
    public static void main(String[] args) {

        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        List<Integer> list = new ArrayList<>();
        for (int i = 0; i < n; i++) {
            list.add(sc.nextInt());
        }
        list.sort(Comparator.naturalOrder());
        int half = n/2-1;
        int result = 0;
        if (list.get(half).equals(list.get(half+1))) {
            System.out.println(result);
            return;
        }
        result = list.get(half+1) - list.get(half);
        System.out.println(result);
    }
} Main public static void main(String[] args) {

        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        List<Integer> list = new ArrayList<>();
        for (int i = 0; i < n; i++) {
            list.add(sc.nextInt());
        }
        list.sort(Comparator.naturalOrder());
        int half = n/2-1;
        int result = 0;
        if (list.get(half).equals(list.get(half+1))) {
            System.out.println(result);
            return;
        }
        result = list.get(half+1) - list.get(half);
        System.out.println(result);
    } main {

        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        List<Integer> list = new ArrayList<>();
        for (int i = 0; i < n; i++) {
            list.add(sc.nextInt());
        }
        list.sort(Comparator.naturalOrder());
        int half = n/2-1;
        int result = 0;
        if (list.get(half).equals(list.get(half+1))) {
            System.out.println(result);
            return;
        }
        result = list.get(half+1) - list.get(half);
        System.out.println(result);
    } Scanner sc = new Scanner(System.in); sc new Scanner(System.in) int n = sc.nextInt(); n sc.nextInt() sc.nextInt sc List<Integer> list = new ArrayList<>(); list new ArrayList<>() for (int i = 0; i < n; i++) {
            list.add(sc.nextInt());
        } int i = 0; int i = 0; i 0 i < n i n i++ i++ i {
            list.add(sc.nextInt());
        } {
            list.add(sc.nextInt());
        } list.add(sc.nextInt()) list.add list sc.nextInt() sc.nextInt sc list.sort(Comparator.naturalOrder()) list.sort list Comparator.naturalOrder() Comparator.naturalOrder Comparator int half = n/2-1; half n/2-1 n/2 n 2 1 int result = 0; result 0 if (list.get(half).equals(list.get(half+1))) {
            System.out.println(result);
            return;
        } list.get(half).equals(list.get(half+1)) list.get(half).equals list.get(half) list.get list half list.get(half+1) list.get list half+1 half 1 {
            System.out.println(result);
            return;
        } System.out.println(result) System.out.println System.out System System.out result return; result = list.get(half+1) - list.get(half) result list.get(half+1) - list.get(half) list.get(half+1) list.get list half+1 half 1 list.get(half) list.get list half System.out.println(result) System.out.println System.out System System.out result String[] args args
import java.util.*;

class Main {
    public static void main(String[] args) {

        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        List<Integer> list = new ArrayList<>();
        for (int i = 0; i < n; i++) {
            list.add(sc.nextInt());
        }
        list.sort(Comparator.naturalOrder());
        int half = n/2-1;
        int result = 0;
        if (list.get(half).equals(list.get(half+1))) {
            System.out.println(result);
            return;
        }
        result = list.get(half+1) - list.get(half);
        System.out.println(result);
    }
}