import java.util.*;

class Main{
  public static void main(String[] args){
    Scanner sc = new Scanner(System.in);
    
    int n = sc.nextInt();
    if(n%2 == 0){
    	int[] d = new int[n];
    	for(int i=0; i<n; i++){
			d[i] = sc.nextInt();
    	}
    

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

    	Arrays.sort(d);
      
    	int ans = d[n/2]-d[n/2-1];
    	System.out.println(ans);
    }
    else{
      System.out.println(0);
    }
  }
} Main public static void main(String[] args){
    Scanner sc = new Scanner(System.in);
    
    int n = sc.nextInt();
    if(n%2 == 0){
    	int[] d = new int[n];
    	for(int i=0; i<n; i++){
			d[i] = sc.nextInt();
    	}
    

    	Arrays.sort(d);
      
    	int ans = d[n/2]-d[n/2-1];
    	System.out.println(ans);
    }
    else{
      System.out.println(0);
    }
  } main {
    Scanner sc = new Scanner(System.in);
    
    int n = sc.nextInt();
    if(n%2 == 0){
    	int[] d = new int[n];
    	for(int i=0; i<n; i++){
			d[i] = sc.nextInt();
    	}
    

    	Arrays.sort(d);
      
    	int ans = d[n/2]-d[n/2-1];
    	System.out.println(ans);
    }
    else{
      System.out.println(0);
    }
  } Scanner sc = new Scanner(System.in); sc new Scanner(System.in) int n = sc.nextInt(); n sc.nextInt() sc.nextInt sc if(n%2 == 0){
    	int[] d = new int[n];
    	for(int i=0; i<n; i++){
			d[i] = sc.nextInt();
    	}
    

    	Arrays.sort(d);
      
    	int ans = d[n/2]-d[n/2-1];
    	System.out.println(ans);
    }
    else{
      System.out.println(0);
    } n%2 == 0 n%2 n 2 0 {
    	int[] d = new int[n];
    	for(int i=0; i<n; i++){
			d[i] = sc.nextInt();
    	}
    

    	Arrays.sort(d);
      
    	int ans = d[n/2]-d[n/2-1];
    	System.out.println(ans);
    } 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 ans = d[n/2]-d[n/2-1]; ans 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 System.out.println(ans) System.out.println System.out System System.out ans {
      System.out.println(0);
    } System.out.println(0) System.out.println System.out System System.out 0 String[] args args
import java.util.*;

class Main{
  public static void main(String[] args){
    Scanner sc = new Scanner(System.in);
    
    int n = sc.nextInt();
    if(n%2 == 0){
    	int[] d = new int[n];
    	for(int i=0; i<n; i++){
			d[i] = sc.nextInt();
    	}
    

    	Arrays.sort(d);
      
    	int ans = d[n/2]-d[n/2-1];
    	System.out.println(ans);
    }
    else{
      System.out.println(0);
    }
  }
}