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 Fortran (gfortran v4.8.4) (judge verdict: Accepted)

program main
implicit none
character*16 :: a
integer :: n,i,j,x,y,z,m
integer,allocatable :: p(:)

read(*,*)n
allocate(p(n))
read(*, *)(p(i), i = 1,n)
call quicksort(p,1,n)

z=0

z = p(n/2+1) - p(n/2)

write(*,*) z

contains 

recursive subroutine quicksort(a, first, last)
  implicit none
  integer  a(*)
  integer first, last
  integer i, j
  real*8  x, t
  
  x = a( (first+last) / 2 )
  i = first
  j = last
  do
     do while (a(i) < x)
        i=i+1
     end do
     do while (x < a(j))
        j=j-1
     end do
     if (i >= j) exit
     t = a(i);  a(i) = a(j);  a(j) = t
     i=i+1
     j=j-1
  end do
  if (first < i - 1) call quicksort(a, first, i - 1)
  if (j + 1 < last)  call quicksort(a, j + 1, last)
end subroutine quicksort
end program main