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: Time Limit Exceeded)

#include <bits/stdc++.h>
using namespace std;
int main() {
  int N;
  cin>>N;
  vector<int> mondai(N);
  for(int i=0; i<N; i++){
    int d;
    cin>>d;
    mondai.at(i)=d;
  }
  sort(mondai.begin(), mondai.end()); //小さいほうから
  int ARC=0;
  int ABC=0;
  int count=0;
  for(int k=1; k<=mondai.at(N-1); k++){
  for(int i=0; i<N; i++){
    if(mondai.at(i)>=k){
      ARC++;
    }
    else{
      ABC++;
    }
    } //i終わり
    if(ARC==ABC){
      count++;
    }
      ARC=0;
      ABC=0;
  } //k終わり
    cout<<count<<endl;
  }