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: Wrong Answer)

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

int Max(int* p, int n) {
    int max=0;
    for(int i=0;i<n;i++) {
        if(p[i]>max) max=p[i];
    }
    return max;
}

int main(void){
    int N;
    int* d;
    int countABC=0,countARC=0,ans=0;
    int max;

    // Nは偶数のみ
    scanf("%d", &N);
    d = malloc(sizeof(int) * N);
    for(int i=0;i<N;i++) scanf("%d", &d[i]);
    max = Max(d, N);

    for(int i=1;i<max;i++) {
        for(int j=0;j<N;j++) {
            if(d[j]<i) countABC++;
            else countARC++;
        }
        if(countABC == countARC) ans++;
        countABC=0; countARC=0;
    }

    printf("%d\n", ans);

    return 0;
}