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++14 (GCC 5.4.1) (judge verdict: Accepted)

#include<bits/stdc++.h>

using namespace std;
#define EPS (1e-7)
#define INF (1e9)
#define PI (acos(-1))

typedef long long  ll;
#define endl '\n'




int dx[4] = {1, 0, -1, 0}, dy[4] = {0, 1, 0, -1};


const int MOD = 1000000007;

//////////////////////////////////////////



int n;

void Input() {

    cin >> n;

}



void Solve() {


    int d[n];
    for(int i = 0; i < n; i++) {

        cin >> d[i];
    }

    sort(d, d+n);

    int r = d[n/2];
    int l = d[n/2 - 1];
    //cout << r << " " << l << endl;

    cout << r - l << endl;

}

int main() {

  cin.tie(0);
  ios::sync_with_stdio(false);
  Input();
  Solve();


  return 0;

}