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: Wrong Answer)

program main
  implicit none
  integer i,N,al,av
  integer,allocatable :: d(:)
  !read(*, *) (L(i), i = 1,N)
  read(*, *) N
  allocate(d(N))
  read(*, *) (d(i), i = 1,N)
  call qsort(d)
  write(*, *) abs(d(N/2)-d(N/2+1)) + 1

  contains

  recursive subroutine qsort(a)
  implicit none
  integer,intent(inout) :: a(:)
  integer :: start,ed,i,j,toobig,toosmall,pv

  n = size(a)
  start = 1
  ed = n
  pv = a((start+ed)/2)
  i = start
  j = ed
  do
     !pv = a((start+ed)/2)
     !i = start
     !j = ed
     do
       if (a(i) < pv) then
         i = i+1
       else
         exit
       end if
     end do
     do
       if(a(j) > pv) then
         j = j-1
       else
         exit
       end if
     end do
     if (i >= j) then
       exit
     else
       toobig = a(i)
       toosmall = a(j)
       a(j) = toobig
       a(i) = toosmall
       i = i + 1
       j = j - 1
     end if
   end do
  if (i-1 > start) then
    call qsort(a(1:i-1))
  end if
  if (j+1 < ed) then
    call qsort(a(j+1:n))
  end if
  end subroutine qsort
  
end program main