Problem:
Score : 300 points

Problem Statement

In some other world, today is Christmas Eve.

There are N trees planted in Mr. Takaha's garden. The height of the i-th tree (1 \leq i \leq N) is h_i meters.

He decides to choose K trees from these trees and decorate them with electric lights. To make the scenery more beautiful, the heights of the decorated trees should be as close to each other as possible.

More specifically, let the height of the tallest decorated tree be h_{max} meters, and the height of the shortest decorated tree be h_{min} meters. The smaller the value h_{max} - h_{min} is, the better. What is the minimum possible value of h_{max} - h_{min}?

Constraints

2 \leq K < N \leq 10^5

1 \leq h_i \leq 10^9

h_i is an integer.

Input

Input is given from Standard Input in the following format:

N K
h_1
h_2
:
h_N

Output

Print the minimum possible value of h_{max} - h_{min}.

Sample Input 1

5 3
10
15
11
14
12

Sample Output 1

2

If we decorate the first, third and fifth trees, h_{max} = 12, h_{min} = 10 so h_{max} - h_{min} = 2. This is optimal.

Sample Input 2

5 3
5
7
5
7
7

Sample Output 2

0

If we decorate the second, fourth and fifth trees, h_{max} = 7, h_{min} = 7 so h_{max} - h_{min} = 0. This is optimal.

There are not too many trees in these sample inputs, but note that there can be at most one hundred thousand trees (we just can't put a sample with a hundred thousand lines here).

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

program main
   implicit none
   integer(8)::n,k,i
   integer(8),allocatable,dimension(:)::h,turn,dummy
   real(8),allocatable,dimension(:)::abss
   real(8)::heikin
   read(*,*)n,k
   allocate(h(n),abss(n),turn(n))
   read(*,*)h
!   heikin=real(sum(h),8)/size(h)
 !  abss=abs(h-heikin)
   call heapsort2(n,h,turn)
   do i=1,n-k
   enddo
   allocate(dummy(n-k+1))
   do i=1,n-k+1
     dummy(i)=abs(h(i)-h(i+k-1))
   enddo
   write(*,*)minval(dummy)
 !  do i=1,k
  !    dummy(i)=h(turn(i))
   !enddo
   !write(*,*)maxval(dummy)-minval(dummy)
   !write(*,*)dummy
contains
subroutine heapsort2(n,array,turn)
  implicit none
  integer(8),intent(in)::n
  integer(8),intent(out)::turn(1:n)
  integer(8),intent(inout)::array(1:n)
  
  integer::i,k,j,l,m
  double precision::t
  
  if(n.le.0)then
     write(6,*)"Error, at heapsort"; stop
  endif
  if(n.eq.1)return

  do i=1,N
     turn(i)=i
  enddo

  l=n/2+1
  k=n
  do while(k.ne.1)
     if(l.gt.1)then
        l=l-1
        t=array(l)
        m=turn(l)
     else
        t=array(k)
        m=turn(k)
        array(k)=array(1)
        turn(k)=turn(1)
        k=k-1
        if(k.eq.1) then
           array(1)=t
           turn(1)=m
           exit
        endif
     endif
     i=l
     j=l+l
     do while(j.le.k)
        if(j.lt.k)then
           if(array(j).lt.array(j+1))j=j+1
        endif
        if (t.lt.array(j))then
           array(i)=array(j)
           turn(i)=turn(j)
           i=j
           j=j+j
        else
           j=k+1
        endif
     enddo
     array(i)=t
     turn(i)=m
  enddo

  return
end subroutine heapsort2
end program main