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