Problem:
Score : 300 points

Problem Statement

Takahashi made N problems for competitive programming.
The problems are numbered 1 to N, and the difficulty of Problem i is represented as an integer d_i (the higher, the harder).

He is dividing the problems into two categories by choosing an integer K, as follows:

A problem with difficulty K or higher will be for ARCs.

A problem with difficulty lower than K will be for ABCs.

How many choices of the integer K make the number of problems for ARCs and the number of problems for ABCs the same?

Problem Statement

2 \leq N \leq 10^5

N is an even number.

1 \leq d_i \leq 10^5

All values in input are integers.

Input

Input is given from Standard Input in the following format:

N
d_1 d_2 ... d_N

Output

Print the number of choices of the integer K that make the number of problems for ARCs and the number of problems for ABCs the same.

Sample Input 1

6
9 1 4 4 6 7

Sample Output 1

2

If we choose K=5 or 6, Problem 1, 5, and 6 will be for ARCs, Problem 2, 3, and 4 will be for ABCs, and the objective is achieved.
Thus, the answer is 2.

Sample Input 2

8
9 1 14 5 5 4 4 14

Sample Output 2

0

There may be no choice of the integer K that make the number of problems for ARCs and the number of problems for ABCs the same.

Sample Input 3

14
99592 10342 29105 78532 83018 11639 92015 77204 30914 21912 34519 80835 100000 1

Sample Output 3

42685

Solution in C (GCC 5.4.1) (judge verdict: Accepted)

  #include <stdio.h>
  #include <stdlib.h>
  #include <string.h>
  int comp(const void *a,const void *b){
    int *x=(int *)a;
    int *y=(int *)b;
    if (*x>*y) {
      return 1;
    }
    if (*x<*y) {
      return -1;
    }
    return 0;
  }

  int main() {
    int n;
    int tab[100000];
    scanf("%d",&n);
    if (n%2) {
      printf("0");
      return 0;
    }
    for (int i = 0; i < n; i++) {
      scanf("%d",&tab[i]);
    }
    qsort(tab,n,sizeof(int),comp);
    printf("%d\n",tab[n/2]-tab[(n/2)-1]); 
    return 0;
  }