import java.util.Arrays;
import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int N = sc.nextInt();
        int[] arr = new int[N];
        for(int i = 0; i < N; i++) arr[i] = sc.nextInt();
        Arrays.sort(arr);
        int mid = N/2;
        int res = 0;
        if(arr[mid] == arr[mid-1]) {
            res = 0;
        } else {
            res = arr[mid] - arr[mid-1];
        }
        System.out.println(res);
    }
} import java.util.Arrays; Arrays java.util import java.util.Scanner; Scanner java.util public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int N = sc.nextInt();
        int[] arr = new int[N];
        for(int i = 0; i < N; i++) arr[i] = sc.nextInt();
        Arrays.sort(arr);
        int mid = N/2;
        int res = 0;
        if(arr[mid] == arr[mid-1]) {
            res = 0;
        } else {
            res = arr[mid] - arr[mid-1];
        }
        System.out.println(res);
    }
} Main public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int N = sc.nextInt();
        int[] arr = new int[N];
        for(int i = 0; i < N; i++) arr[i] = sc.nextInt();
        Arrays.sort(arr);
        int mid = N/2;
        int res = 0;
        if(arr[mid] == arr[mid-1]) {
            res = 0;
        } else {
            res = arr[mid] - arr[mid-1];
        }
        System.out.println(res);
    } main {
        Scanner sc = new Scanner(System.in);
        int N = sc.nextInt();
        int[] arr = new int[N];
        for(int i = 0; i < N; i++) arr[i] = sc.nextInt();
        Arrays.sort(arr);
        int mid = N/2;
        int res = 0;
        if(arr[mid] == arr[mid-1]) {
            res = 0;
        } else {
            res = arr[mid] - arr[mid-1];
        }
        System.out.println(res);
    } Scanner sc = new Scanner(System.in); sc new Scanner(System.in) int N = sc.nextInt(); N sc.nextInt() sc.nextInt sc int[] arr = new int[N]; arr new int[N] N for(int i = 0; i < N; i++) arr[i] = sc.nextInt(); int i = 0; int i = 0; i 0 i < N i N i++ i++ i arr[i] = sc.nextInt(); arr[i] = sc.nextInt() arr[i] arr i sc.nextInt() sc.nextInt sc Arrays.sort(arr) Arrays.sort Arrays arr int mid = N/2; mid N/2 N 2 int res = 0; res 0 if(arr[mid] == arr[mid-1]) {
            res = 0;
        } else {
            res = arr[mid] - arr[mid-1];
        } arr[mid] == arr[mid-1] arr[mid] arr mid arr[mid-1] arr mid-1 mid 1 {
            res = 0;
        } res = 0 res 0 {
            res = arr[mid] - arr[mid-1];
        } res = arr[mid] - arr[mid-1] res arr[mid] - arr[mid-1] arr[mid] arr mid arr[mid-1] arr mid-1 mid 1 System.out.println(res) System.out.println System.out System System.out res String[] args args public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int N = sc.nextInt();
        int[] arr = new int[N];
        for(int i = 0; i < N; i++) arr[i] = sc.nextInt();
        Arrays.sort(arr);
        int mid = N/2;
        int res = 0;
        if(arr[mid] == arr[mid-1]) {
            res = 0;
        } else {
            res = arr[mid] - arr[mid-1];
        }
        System.out.println(res);
    }
} public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int N = sc.nextInt();
        int[] arr = new int[N];
        for(int i = 0; i < N; i++) arr[i] = sc.nextInt();
        Arrays.sort(arr);
        int mid = N/2;
        int res = 0;
        if(arr[mid] == arr[mid-1]) {
            res = 0;
        } else {
            res = arr[mid] - arr[mid-1];
        }
        System.out.println(res);
    }
} Main
import java.util.Arrays;
import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int N = sc.nextInt();
        int[] arr = new int[N];
        for(int i = 0; i < N; i++) arr[i] = sc.nextInt();
        Arrays.sort(arr);
        int mid = N/2;
        int res = 0;
        if(arr[mid] == arr[mid-1]) {
            res = 0;
        } else {
            res = arr[mid] - arr[mid-1];
        }
        System.out.println(res);
    }
}
