program successive_subtraction
  implicit none
  integer :: n, i
  integer(8) :: a(100000), m
  a = 0_8
  read(*,*) n
  read(*,*) a(1:n)
  call merge_sort(n,a(1:n))
  if (mod(n,2).eq.1) then
    m = a(n)
    do i = 1, n/2
      m = m+a(n-i)-a(i)
    end do
    write(*,'(i0)') m
    do i = 1, n/2
      write(*,'(i0,x,i0)') a(i), a(n-i)
    end do
    m = a(n)
    do i = 1, n/2
      write(*,'(i0,x,i0)') m, a(i)-a(n-i)
      m = m+a(n-i)-a(i)
    end do
  else
    m = a(n)-a(1)
    do i = 2, n/2
      m = m+a(n-i+1)-a(i)
    end do
    write(*,'(i0)') m
    write(*,'(i0)') a(n), a(1)
    do i = 2, n/2
      write(*,'(i0,x,i0)') a(i), a(n-i+1)
    end do
    m = a(n)-a(1)
    do i = 2, n/2
      write(*,'(i0,x,i0)') m, a(i)-a(n-i+1)
      m = m+a(n-i+1)-a(i)
    end do
  end if
  stop
contains
  subroutine merge_sort(n,c)
    implicit none
    integer, intent(in) :: n
    integer(8), intent(inout) :: c(n)
    integer :: m, l, i, u
    m = n
    l = 1
    do while (m.gt.1)
      do i = 1, m/2
        u = min(2*i*l,n)
        call merge(c(2*(i-1)*l+1:(2*i-1)*l),c((2*i-1)*l+1:u))
      end do
      l = 2*l
      m = (m+1)/2
    end do
    return
  end subroutine merge_sort
  subroutine merge(c1,c2)
    implicit none
    integer(8), intent(inout) :: c1(:), c2(:)
    integer(8) :: c(size(c1)+size(c2))
    integer :: i1, i2, n1, n2
    i1 = 1
    i2 = 1
    n1 = size(c1)
    n2 = size(c2)
    do while (i1.le.n1.and.i2.le.n2)
      if (c1(i1).le.c2(i2)) then
        c(i1+i2-1) = c1(i1)
        i1 = i1+1
      else
        c(i1+i2-1) = c2(i2)
        i2 = i2+1
       end if
    end do
    if (i1.le.n1) then
      c(i1+i2-1:n1+n2) = c1(i1:n1)
    else if (i2.le.n2) then
      c(i1+i2-1:n1+n2) = c2(i2:n2)
    end if
    c1 = c(1:n1)
    c2 = c(n1+1:n1+n2)
    return
  end subroutine merge
end program successive_subtraction