import java.util.*;

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

public class Main {
  public static void main(String[] args) {
    Scanner sc = new Scanner(System.in);
    int N = sc.nextInt();
    int A[] = new int[N];
    int counter = 0;
    
    for(int i=0; i<N; i++) {
      A[i] = sc.nextInt();
    }
    Arrays.sort(A);
    
    for(int j=N/2; j<N; j++){
      if(A[j] > A[N/2 - 1]) {
        break;
      } else if(A[j] == A[N/2-1]) {
        counter++;
      }
    }
    if(counter>1){
      System.out.println(0);
    } else {
      System.out.println(A[N/2] - A[N/2-1]);
    }
  }
}