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)

// https://atcoder.jp/contests/abc132/tasks/abc132_c

#include <stdio.h>
#include <stdlib.h>
#define forn(i,L,R) for (int i = L; i < R; i++)
#define wez(n) int (n); scanf("%d",&(n))
#define getInt(a) scanf("%d", &a)

int cmpfunc (const void * a, const void * b) {
   return ( *(int*)a - *(int*)b );
}

int main(){
    wez(n);
    int arr[100000];
    forn(i, 0, n)
        getInt(arr[i]);
    qsort(arr, n, sizeof(int), cmpfunc);
    printf("%d\n", arr[n/2] - arr[n/2 - 1]);
}