import java.util.*;

public class Main {
    public static void main(String[] args) {
	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);
	int f = d[n/2 - 1];
	int l = d[n/2];
	//f->×,l->〇
	System.out.print(l-f);
    }
} import java.util.*; util.* java public class Main {
    public static void main(String[] args) {
	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);
	int f = d[n/2 - 1];
	int l = d[n/2];
	//f->×,l->〇
	System.out.print(l-f);
    }
} Main public static void main(String[] args) {
	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);
	int f = d[n/2 - 1];
	int l = d[n/2];
	//f->×,l->〇
	System.out.print(l-f);
    } main {
	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);
	int f = d[n/2 - 1];
	int l = d[n/2];
	//f->×,l->〇
	System.out.print(l-f);
    } 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 int f = d[n/2 - 1]; f d[n/2 - 1] d n/2 - 1 n/2 n 2 1 int l = d[n/2]; l d[n/2] d n/2 n 2 System.out.print(l-f) System.out.print System.out System System.out l-f l f String[] args args public class Main {
    public static void main(String[] args) {
	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);
	int f = d[n/2 - 1];
	int l = d[n/2];
	//f->×,l->〇
	System.out.print(l-f);
    }
} public class Main {
    public static void main(String[] args) {
	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);
	int f = d[n/2 - 1];
	int l = d[n/2];
	//f->×,l->〇
	System.out.print(l-f);
    }
} Main
import java.util.*;

public class Main {
    public static void main(String[] args) {
	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);
	int f = d[n/2 - 1];
	int l = d[n/2];
	//f->×,l->〇
	System.out.print(l-f);
    }
}
