import java.io.*;
import java.util.*;
public class Main {
    public static void main(String[] args) {
        Scanner scan = new Scanner(System.in);
        int N = scan.nextInt();
        int [] d = new int [N];
        for(int i=0;i<N;i++){
            d[i] = scan.nextInt();
        }
        quick_sort(d,0,N-1);
        if(d[(N/2)-1]==d[N/2]){
            System.out.println("0");
        }else{
            System.out.println(d[N/2]-d[(N/2)-1]);
        }
    }
    static void quick_sort(int[] d, int left, int right) {
        if (left >= right) {
            return;
        }
        int p = d[(left + right) / 2];
        int l = left, r = right, tmp;
        while (l <= r) {
            while (d[l] < p) {
                l++;
            }
            while (d[r] > p) {
                r--;
            }
            if (l <= r) {
                tmp = d[l];
                d[l] = d[r];
                d[r] = tmp;
                l++;
                r--;
            }
        }
        quick_sort(d, left, r);
        quick_sort(d, l, right);
    }
} import java.io.*; io.* java import java.util.*; util.* java public class Main {
    public static void main(String[] args) {
        Scanner scan = new Scanner(System.in);
        int N = scan.nextInt();
        int [] d = new int [N];
        for(int i=0;i<N;i++){
            d[i] = scan.nextInt();
        }
        quick_sort(d,0,N-1);
        if(d[(N/2)-1]==d[N/2]){
            System.out.println("0");
        }else{
            System.out.println(d[N/2]-d[(N/2)-1]);
        }
    }
    static void quick_sort(int[] d, int left, int right) {
        if (left >= right) {
            return;
        }
        int p = d[(left + right) / 2];
        int l = left, r = right, tmp;
        while (l <= r) {
            while (d[l] < p) {
                l++;
            }
            while (d[r] > p) {
                r--;
            }
            if (l <= r) {
                tmp = d[l];
                d[l] = d[r];
                d[r] = tmp;
                l++;
                r--;
            }
        }
        quick_sort(d, left, r);
        quick_sort(d, l, right);
    }
} Main public static void main(String[] args) {
        Scanner scan = new Scanner(System.in);
        int N = scan.nextInt();
        int [] d = new int [N];
        for(int i=0;i<N;i++){
            d[i] = scan.nextInt();
        }
        quick_sort(d,0,N-1);
        if(d[(N/2)-1]==d[N/2]){
            System.out.println("0");
        }else{
            System.out.println(d[N/2]-d[(N/2)-1]);
        }
    } main {
        Scanner scan = new Scanner(System.in);
        int N = scan.nextInt();
        int [] d = new int [N];
        for(int i=0;i<N;i++){
            d[i] = scan.nextInt();
        }
        quick_sort(d,0,N-1);
        if(d[(N/2)-1]==d[N/2]){
            System.out.println("0");
        }else{
            System.out.println(d[N/2]-d[(N/2)-1]);
        }
    } Scanner scan = new Scanner(System.in); scan new Scanner(System.in) int N = scan.nextInt(); N scan.nextInt() scan.nextInt scan int [] d = new int [N]; d new int [N] N for(int i=0;i<N;i++){
            d[i] = scan.nextInt();
        } int i=0; int i=0; i 0 i<N i N i++ i++ i {
            d[i] = scan.nextInt();
        } {
            d[i] = scan.nextInt();
        } d[i] = scan.nextInt() d[i] d i scan.nextInt() scan.nextInt scan quick_sort(d,0,N-1) quick_sort d 0 N-1 N 1 if(d[(N/2)-1]==d[N/2]){
            System.out.println("0");
        }else{
            System.out.println(d[N/2]-d[(N/2)-1]);
        } d[(N/2)-1]==d[N/2] d[(N/2)-1] d (N/2)-1 (N/2) N 2 1 d[N/2] d N/2 N 2 {
            System.out.println("0");
        } System.out.println("0") System.out.println System.out System System.out "0" {
            System.out.println(d[N/2]-d[(N/2)-1]);
        } 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 String[] args args static void quick_sort(int[] d, int left, int right) {
        if (left >= right) {
            return;
        }
        int p = d[(left + right) / 2];
        int l = left, r = right, tmp;
        while (l <= r) {
            while (d[l] < p) {
                l++;
            }
            while (d[r] > p) {
                r--;
            }
            if (l <= r) {
                tmp = d[l];
                d[l] = d[r];
                d[r] = tmp;
                l++;
                r--;
            }
        }
        quick_sort(d, left, r);
        quick_sort(d, l, right);
    } quick_sort {
        if (left >= right) {
            return;
        }
        int p = d[(left + right) / 2];
        int l = left, r = right, tmp;
        while (l <= r) {
            while (d[l] < p) {
                l++;
            }
            while (d[r] > p) {
                r--;
            }
            if (l <= r) {
                tmp = d[l];
                d[l] = d[r];
                d[r] = tmp;
                l++;
                r--;
            }
        }
        quick_sort(d, left, r);
        quick_sort(d, l, right);
    } if (left >= right) {
            return;
        } left >= right left right {
            return;
        } return; int p = d[(left + right) / 2]; p d[(left + right) / 2] d (left + right) / 2 (left + right) left right 2 int l = left l left r = right r right tmp; tmp while (l <= r) {
            while (d[l] < p) {
                l++;
            }
            while (d[r] > p) {
                r--;
            }
            if (l <= r) {
                tmp = d[l];
                d[l] = d[r];
                d[r] = tmp;
                l++;
                r--;
            }
        } l <= r l r {
            while (d[l] < p) {
                l++;
            }
            while (d[r] > p) {
                r--;
            }
            if (l <= r) {
                tmp = d[l];
                d[l] = d[r];
                d[r] = tmp;
                l++;
                r--;
            }
        } while (d[l] < p) {
                l++;
            } d[l] < p d[l] d l p {
                l++;
            } l++ l while (d[r] > p) {
                r--;
            } d[r] > p d[r] d r p {
                r--;
            } r-- r if (l <= r) {
                tmp = d[l];
                d[l] = d[r];
                d[r] = tmp;
                l++;
                r--;
            } l <= r l r {
                tmp = d[l];
                d[l] = d[r];
                d[r] = tmp;
                l++;
                r--;
            } tmp = d[l] tmp d[l] d l d[l] = d[r] d[l] d l d[r] d r d[r] = tmp d[r] d r tmp l++ l r-- r quick_sort(d, left, r) quick_sort d left r quick_sort(d, l, right) quick_sort d l right int[] d d int left left int right right public class Main {
    public static void main(String[] args) {
        Scanner scan = new Scanner(System.in);
        int N = scan.nextInt();
        int [] d = new int [N];
        for(int i=0;i<N;i++){
            d[i] = scan.nextInt();
        }
        quick_sort(d,0,N-1);
        if(d[(N/2)-1]==d[N/2]){
            System.out.println("0");
        }else{
            System.out.println(d[N/2]-d[(N/2)-1]);
        }
    }
    static void quick_sort(int[] d, int left, int right) {
        if (left >= right) {
            return;
        }
        int p = d[(left + right) / 2];
        int l = left, r = right, tmp;
        while (l <= r) {
            while (d[l] < p) {
                l++;
            }
            while (d[r] > p) {
                r--;
            }
            if (l <= r) {
                tmp = d[l];
                d[l] = d[r];
                d[r] = tmp;
                l++;
                r--;
            }
        }
        quick_sort(d, left, r);
        quick_sort(d, l, right);
    }
} public class Main {
    public static void main(String[] args) {
        Scanner scan = new Scanner(System.in);
        int N = scan.nextInt();
        int [] d = new int [N];
        for(int i=0;i<N;i++){
            d[i] = scan.nextInt();
        }
        quick_sort(d,0,N-1);
        if(d[(N/2)-1]==d[N/2]){
            System.out.println("0");
        }else{
            System.out.println(d[N/2]-d[(N/2)-1]);
        }
    }
    static void quick_sort(int[] d, int left, int right) {
        if (left >= right) {
            return;
        }
        int p = d[(left + right) / 2];
        int l = left, r = right, tmp;
        while (l <= r) {
            while (d[l] < p) {
                l++;
            }
            while (d[r] > p) {
                r--;
            }
            if (l <= r) {
                tmp = d[l];
                d[l] = d[r];
                d[r] = tmp;
                l++;
                r--;
            }
        }
        quick_sort(d, left, r);
        quick_sort(d, l, right);
    }
} Main
import java.io.*;
import java.util.*;
public class Main {
    public static void main(String[] args) {
        Scanner scan = new Scanner(System.in);
        int N = scan.nextInt();
        int [] d = new int [N];
        for(int i=0;i<N;i++){
            d[i] = scan.nextInt();
        }
        quick_sort(d,0,N-1);
        if(d[(N/2)-1]==d[N/2]){
            System.out.println("0");
        }else{
            System.out.println(d[N/2]-d[(N/2)-1]);
        }
    }
    static void quick_sort(int[] d, int left, int right) {
        if (left >= right) {
            return;
        }
        int p = d[(left + right) / 2];
        int l = left, r = right, tmp;
        while (l <= r) {
            while (d[l] < p) {
                l++;
            }
            while (d[r] > p) {
                r--;
            }
            if (l <= r) {
                tmp = d[l];
                d[l] = d[r];
                d[r] = tmp;
                l++;
                r--;
            }
        }
        quick_sort(d, left, r);
        quick_sort(d, l, right);
    }
}