import java.util.*;
import java.math.*;
public class Main {
    static final int MOD = 1_000_000_007; // 10^9+7
    //static final int MAX = 2_147_483_646; // intの最大値
    static final int INF = 1_000_000_000; // 10^9
    static final int MAX = 10_000_000;
    public static void main(String args[]) {
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        int[] ary = new int[n];
        for(int i = 0;i < n;i++){
            ary[i] = sc.nextInt();
        }
        Arrays.sort(ary);
        System.out.println(ary[n/2]-ary[n/2-1]);
    }       
}



 import java.util.*; util.* java import java.math.*; math.* java public class Main {
    static final int MOD = 1_000_000_007; // 10^9+7
    //static final int MAX = 2_147_483_646; // intの最大値
    static final int INF = 1_000_000_000; // 10^9
    static final int MAX = 10_000_000;
    public static void main(String args[]) {
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        int[] ary = new int[n];
        for(int i = 0;i < n;i++){
            ary[i] = sc.nextInt();
        }
        Arrays.sort(ary);
        System.out.println(ary[n/2]-ary[n/2-1]);
    }       
} Main static final int MOD = 1_000_000_007; // 10^9+7 MOD 1_000_000_007 //static final int MAX = 2_147_483_646; // intの最大値
    static final int INF = 1_000_000_000; // 10^9 INF 1_000_000_000 static final int MAX = 10_000_000; MAX 10_000_000 public static void main(String args[]) {
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        int[] ary = new int[n];
        for(int i = 0;i < n;i++){
            ary[i] = sc.nextInt();
        }
        Arrays.sort(ary);
        System.out.println(ary[n/2]-ary[n/2-1]);
    } main {
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        int[] ary = new int[n];
        for(int i = 0;i < n;i++){
            ary[i] = sc.nextInt();
        }
        Arrays.sort(ary);
        System.out.println(ary[n/2]-ary[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[] ary = new int[n]; ary new int[n] n for(int i = 0;i < n;i++){
            ary[i] = sc.nextInt();
        } int i = 0; int i = 0; i 0 i < n i n i++ i++ i {
            ary[i] = sc.nextInt();
        } {
            ary[i] = sc.nextInt();
        } ary[i] = sc.nextInt() ary[i] ary i sc.nextInt() sc.nextInt sc Arrays.sort(ary) Arrays.sort Arrays ary System.out.println(ary[n/2]-ary[n/2-1]) System.out.println System.out System System.out ary[n/2]-ary[n/2-1] ary[n/2] ary n/2 n 2 ary[n/2-1] ary n/2-1 n/2 n 2 1 String args[] args public class Main {
    static final int MOD = 1_000_000_007; // 10^9+7
    //static final int MAX = 2_147_483_646; // intの最大値
    static final int INF = 1_000_000_000; // 10^9
    static final int MAX = 10_000_000;
    public static void main(String args[]) {
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        int[] ary = new int[n];
        for(int i = 0;i < n;i++){
            ary[i] = sc.nextInt();
        }
        Arrays.sort(ary);
        System.out.println(ary[n/2]-ary[n/2-1]);
    }       
} public class Main {
    static final int MOD = 1_000_000_007; // 10^9+7
    //static final int MAX = 2_147_483_646; // intの最大値
    static final int INF = 1_000_000_000; // 10^9
    static final int MAX = 10_000_000;
    public static void main(String args[]) {
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        int[] ary = new int[n];
        for(int i = 0;i < n;i++){
            ary[i] = sc.nextInt();
        }
        Arrays.sort(ary);
        System.out.println(ary[n/2]-ary[n/2-1]);
    }       
} Main
import java.util.*;
import java.math.*;
public class Main {
    static final int MOD = 1_000_000_007; // 10^9+7
    //static final int MAX = 2_147_483_646; // intの最大値
    static final int INF = 1_000_000_000; // 10^9
    static final int MAX = 10_000_000;
    public static void main(String args[]) {
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        int[] ary = new int[n];
        for(int i = 0;i < n;i++){
            ary[i] = sc.nextInt();
        }
        Arrays.sort(ary);
        System.out.println(ary[n/2]-ary[n/2-1]);
    }       
}




