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 Python (3.4.3) (judge verdict: Runtime Error)

def quick_sort(arr):
    left = []
    right = []
    if len(arr) <= 1:
        return arr

    # データの状態に左右されないためにrandom.choice()を用いることもある。
    # ref = random.choice(arr)
    ref = arr[0]
    ref_count = 0

    for ele in arr:
        if ele < ref:
            left.append(ele)
        elif ele > ref:
            right.append(ele)
        else:
            ref_count += 1
    left = quick_sort(left)
    right = quick_sort(right)
    return left + [ref] * ref_count + right

n=input()
S=list(input().split())
for i in S:
    i=int(i)
S=quick_sort(S)
word=int(int(n)/2)
print(S)
s=int(S[word])-int(S[word-1])
s2=int(S[word+1])-int(S[word])
print(s)