import java.util.*;

public class Main {

    long INF = Long.MAX_VALUE;
    long[][] dp;
    int MAX_M = 100000;
    int MAX_N = 100000;

    public static void main(String[] args) {
        new Main().solve();
    }

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

    long INF = Long.MAX_VALUE;
    long[][] dp;
    int MAX_M = 100000;
    int MAX_N = 100000;

    public static void main(String[] args) {
        new Main().solve();
    }

    void solve() {
        Scanner sc = new Scanner(System.in);
        int N = sc.nextInt();
        int[] d = new int[N];
        for(int i = 0;i < N;i++){
            d[i] = sc.nextInt();
        }
        Arrays.sort(d);
        System.out.println(d[N/2]-d[N/2-1]);
    }
} Main long INF = Long.MAX_VALUE; INF Long.MAX_VALUE Long Long.MAX_VALUE long[][] dp; dp int MAX_M = 100000; MAX_M 100000 int MAX_N = 100000; MAX_N 100000 public static void main(String[] args) {
        new Main().solve();
    } main {
        new Main().solve();
    } new Main().solve() new Main().solve new Main() String[] args args void solve() {
        Scanner sc = new Scanner(System.in);
        int N = sc.nextInt();
        int[] d = new int[N];
        for(int i = 0;i < N;i++){
            d[i] = sc.nextInt();
        }
        Arrays.sort(d);
        System.out.println(d[N/2]-d[N/2-1]);
    } solve {
        Scanner sc = new Scanner(System.in);
        int N = sc.nextInt();
        int[] d = new int[N];
        for(int i = 0;i < N;i++){
            d[i] = sc.nextInt();
        }
        Arrays.sort(d);
        System.out.println(d[N/2]-d[N/2-1]);
    } Scanner sc = new Scanner(System.in); sc new Scanner(System.in) int N = sc.nextInt(); N sc.nextInt() sc.nextInt sc int[] d = new int[N]; d new int[N] N for(int i = 0;i < N;i++){
            d[i] = sc.nextInt();
        } int i = 0; int i = 0; i 0 i < N i N i++ i++ i {
            d[i] = sc.nextInt();
        } {
            d[i] = sc.nextInt();
        } d[i] = sc.nextInt() d[i] d i sc.nextInt() sc.nextInt sc Arrays.sort(d) Arrays.sort Arrays d System.out.println(d[N/2]-d[N/2-1]) System.out.println System.out System System.out d[N/2]-d[N/2-1] d[N/2] d N/2 N 2 d[N/2-1] d N/2-1 N/2 N 2 1 public class Main {

    long INF = Long.MAX_VALUE;
    long[][] dp;
    int MAX_M = 100000;
    int MAX_N = 100000;

    public static void main(String[] args) {
        new Main().solve();
    }

    void solve() {
        Scanner sc = new Scanner(System.in);
        int N = sc.nextInt();
        int[] d = new int[N];
        for(int i = 0;i < N;i++){
            d[i] = sc.nextInt();
        }
        Arrays.sort(d);
        System.out.println(d[N/2]-d[N/2-1]);
    }
} public class Main {

    long INF = Long.MAX_VALUE;
    long[][] dp;
    int MAX_M = 100000;
    int MAX_N = 100000;

    public static void main(String[] args) {
        new Main().solve();
    }

    void solve() {
        Scanner sc = new Scanner(System.in);
        int N = sc.nextInt();
        int[] d = new int[N];
        for(int i = 0;i < N;i++){
            d[i] = sc.nextInt();
        }
        Arrays.sort(d);
        System.out.println(d[N/2]-d[N/2-1]);
    }
} Main
import java.util.*;

public class Main {

    long INF = Long.MAX_VALUE;
    long[][] dp;
    int MAX_M = 100000;
    int MAX_N = 100000;

    public static void main(String[] args) {
        new Main().solve();
    }

    void solve() {
        Scanner sc = new Scanner(System.in);
        int N = sc.nextInt();
        int[] d = new int[N];
        for(int i = 0;i < N;i++){
            d[i] = sc.nextInt();
        }
        Arrays.sort(d);
        System.out.println(d[N/2]-d[N/2-1]);
    }
}