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 <stdio.h>
#include <stdlib.h>
#include <string.h>

#include <iostream>
#include <string>
#include <vector>
#include <map>
#include <unordered_map>
#include <queue>
#include <algorithm>

#include <bits/stdc++.h>
#include <cmath>
#include <limits>

using namespace std;

int main(int argc, char* argv[]){
	cin.tie(0);
	ios::sync_with_stdio(false);

	int N;
	vector<int> vd;

	cin >> N;
	for(int i=0; i<N; i++){
		int d;
		cin >> d;
		vd.push_back(d);
	}

	sort(vd.begin(), vd.end());

	int r = N / 2 ;
	int l = r - 1;
	int ans = vd[r] - vd[l];
	cout << ans << endl ;
	return 0;
}