program divide_the_problems
  implicit none
  integer :: n, d(100000), m, i
  d = 0
  read(*,*) n
  read(*,*) d(1:n)
  call quick_sort(d(1:n))
  write(*,'(i0)') d(n/2+1)-d(n/2)
  stop
contains
  recursive subroutine quick_sort(a)
    implicit none
    integer, intent(inout) :: a(:)
    integer :: p, c
    integer :: n, l, r
    n = size(a)
    l = 1
    r = n
    p = a((l+r)/2)+a(l)+a(r)-max(a((l+r)/2),a(l),a(r))-min(a((l+r)/2),a(l),a(r))
    do
      do while (a(l).lt.p)
        l = l+1
      end do
      do while (a(r).gt.p)
        r = r-1
      end do
      if (l.ge.r) exit
      c = a(l)
      a(l) = a(r)
      a(r) = c
      l = l+1
      r = r-1
    end do
    if (l.gt.2) call quick_sort(a(1:l-1))
    if (n.gt.r+1) call quick_sort(a(r+1:n))
  end subroutine quick_sort
end program divide_the_problems