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<stdint.h>
#include<inttypes.h>

typedef int32_t i32;

#define ALLOC(size,type) ((type*)calloc((size),sizeof(type)))
#define SORT(a,num,cmp) qsort((a),(num),sizeof(*(a)),cmp)

int cmp_int (const void *a, const void *b) {
  i32 d = *(i32 *)a - *(i32 *)b;
  return d == 0 ? 0 : d < 0 ? -1 : 1;
}

void run (void) {
  i32 n;
  scanf ("%" SCNi32, &n);
  i32 *d = ALLOC (n, i32);
  for (i32 i = 0; i < n; ++i) {
    scanf ("%" SCNi32, d + i);
  }
  SORT (d, n, cmp_int);
  i32 ans = d[n / 2] - d[n / 2 - 1];
  printf ("%" PRIi32 "\n", ans);
}

int main (void) {
  run();
  return 0;
}