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: Wrong Answer)

#include <iostream>
#include <cmath>
#include <vector>
#include <algorithm> // sort
using namespace std;

int main(void){
    int n; cin >> n;
    vector<int> d(n);
    for(int i=0; i<n; i++){
        cin >> d[i];
    }

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

    if(d[n/2]==d[(n/2)-1]) cout << 0;
    else if(d[(n/2)-1] == d[(n/2)-2] && d[(n/2)+1] == d[(n/2)+2]) cout << d[n/2]-d[n/2-1]-2;
    else if(d[(n/2)-1] == d[(n/2)-2]) cout << d[n/2]-d[n/2-1];
    else if(d[(n/2)+1] == d[(n/2)+2]) cout << d[n/2]-d[n/2-1];
    else cout << d[n/2]-d[n/2-1]+1;
    
    return 0;
}