Problem:
Score : 500 points

Problem Statement

We have a grid with H horizontal rows and W vertical columns. Let (i,j) denote the square at the i-th row from the top and the j-th column from the left.

The square (i, j) has two numbers A_{ij} and B_{ij} written on it.

First, for each square, Takahashi paints one of the written numbers red and the other blue.

Then, he travels from the square (1, 1) to the square (H, W). In one move, he can move from a square (i, j) to the square (i+1, j) or the square (i, j+1). He must not leave the grid.

Let the unbalancedness be the absolute difference of the sum of red numbers and the sum of blue numbers written on the squares along Takahashi's path, including the squares (1, 1) and (H, W).

Takahashi wants to make the unbalancedness as small as possible by appropriately painting the grid and traveling on it.

Find the minimum unbalancedness possible.

Constraints

2 \leq H \leq 80

2 \leq W \leq 80

0 \leq A_{ij} \leq 80

0 \leq B_{ij} \leq 80

All values in input are integers.

Input

Input is given from Standard Input in the following format:

H W
A_{11} A_{12} \ldots A_{1W}
:
A_{H1} A_{H2} \ldots A_{HW}
B_{11} B_{12} \ldots B_{1W}
:
B_{H1} B_{H2} \ldots B_{HW}

Output

Print the minimum unbalancedness possible.

Sample Input 1

2 2
1 2
3 4
3 4
2 1

Sample Output 1

0

By painting the grid and traveling on it as shown in the figure below, the sum of red numbers and the sum of blue numbers are 3+3+1=7 and 1+2+4=7, respectively, for the unbalancedness of 0.

Sample Input 2

2 3
1 10 80
80 10 1
1 2 3
4 5 6

Sample Output 2

2

Solution in Fortran (GNU Fortran 9.2.1) (judge verdict: Accepted)

module mod_bitset
  implicit none
  integer, private, parameter :: address_bits_per_word = 6
  integer, private, parameter :: bits_per_word = lshift(1, address_bits_per_word)
  integer, private, parameter :: bit_index_mask = bits_per_word - 1
  integer(8), private, parameter :: word_mask = -1
  type t_bitset
    integer(8), private, allocatable :: words(:) ! 0-indexed, [start, end)
    integer, private :: words_in_use = 0
  contains
    procedure, private :: flip0
    procedure, private :: flip1
    generic :: flip => flip0, flip1
    procedure, private :: set0
    procedure, private :: set1
    procedure, private :: setval0
    procedure, private :: setval1
    generic :: set => set0, set1, setval0, setval1
    procedure, private :: clear0
    procedure, private :: clear1
    procedure, private :: clear2
    generic :: clear => clear0, clear1, clear2
    procedure, private :: get0
    procedure, private :: get1
    generic :: get => get0, get1
    procedure :: next_set_bit => next_set_bit
    procedure :: next_clear_bit => next_clear_bit
    procedure :: previous_set_bit => previous_set_bit
    procedure :: previous_clear_bit => previous_clear_bit
    procedure :: length => length
    procedure :: is_empty => is_empty
    procedure :: is_not_empty => is_not_empty
    procedure :: intersects => intersects
    procedure :: cardinality => cardinality
    procedure :: and => and0
    procedure :: or => or0
    procedure :: xor => xor0
    procedure :: and_not => and_not0
    procedure :: size => size0
  end type
  interface bitset
    module procedure :: newb0, newb3
  end interface bitset
  interface slshift
    module procedure :: slshift0, slshift1
  end interface slshift
  interface urshift
    module procedure :: urshift0, urshift1
  end interface urshift
contains
  integer function slshift0(i, n) result(res)
    integer, intent(in) :: i
    integer, intent(in) :: n
    integer :: m
    m = and(n, 31)
    res = lshift(i, m)
  end
  integer(8) function slshift1(i, n) result(res)
    integer(8), intent(in) :: i
    integer, intent(in) :: n
    integer :: m
    m = and(n, 63)
    res = lshift(i, m)
  end
  integer function urshift0(i, n) result(res)
    integer, intent(in) :: i
    integer, intent(in) :: n
    integer :: m
    m = and(n, 31)
    if (m == 0) then
      res = i
    else
      res = rshift(ibclr(rshift(i, 1), 31), m - 1)
    end if
  end
  integer(8) function urshift1(i, n) result(res)
    integer(8), intent(in) :: i
    integer, intent(in) :: n
    integer :: m
    m = and(n, 63)
    if (m == 0) then
      res = i
    else
      res = rshift(ibclr(rshift(i, 1), 63), m - 1)
    end if
  end
  integer function number_of_leading_zeros(i) result(res)
    integer(8), intent(in) :: i
    integer :: x
    if (i == 0) then
      res = 64
      return
    end if
    res = 1
    x = int(urshift(i, 32))
    if (x == 0) then
      res = res + 32
      x = int(i)
    end if
    if (urshift(x, 16) == 0) then
      res = res + 16
      x = lshift(x, 16)
    end if
    if (urshift(x, 24) == 0) then
      res = res + 8
      x = lshift(x, 8)
    end if
    if (urshift(x, 28) == 0) then
      res = res + 4
      x = lshift(x, 4)
    end if
    if (urshift(x, 30) == 0) then
      res = res + 2
      x = lshift(x, 2)
    end if
    res = res - urshift(x, 31)
  end
  integer function number_of_trailing_zeros(i) result(res)
    integer(8), intent(in) :: i
    integer :: x, y
    if (i == 0) then
      res = 64
      return
    end if
    res = 63
    y = int(i)
    if (y /= 0) then
      res = res - 32
      x = y
    else
      x = int(urshift(i, 32))
    end if
    y = lshift(x, 16)
    if (y /= 0) then
      res = res - 16
      x = y
    end if
    if (y /= 0) then
      res = res - 8
      x = y
    end if
    if (y /= 0) then
      res = res - 4
      x = y
    end if
    if (y /= 0) then
      res = res - 2
      x = y
    end if
    res = res - urshift(lshift(x, 1), 31)
  end
  integer function words_index(bit_index) result(res)
    integer, intent(in) :: bit_index
    res = rshift(bit_index, address_bits_per_word)
  end
  subroutine assert(flag, message)
    logical, intent(in) :: flag
    character(*), intent(in), optional :: message
    if (flag) return
    write(*,*) "*** Error occurred ***"
    if (present(message)) write(*,'(a)') message
    stop
  end
  subroutine check_invariants(this)
    type(t_bitset), intent(in) :: this
    integer :: u, n
    u = this%words_in_use
    n = size(this%words)
    if (u /= 0) call assert(this%words(u - 1) /= 0, "At check_invariants() (1)")
    call assert(u >= 0 .and. u <= n, "At check_invariants() (2)")
    if (u /= n) call assert(this%words(u) == 0, "At check_invariants() (3)")
  end
  subroutine recalculate_words_in_use(this)
    type(t_bitset), intent(inout) :: this
    integer :: i
    do i = this%words_in_use - 1, 0, -1
      if (this%words(i) /= 0) then
        this%words_in_use = i + 1
        return
      end if
    end do
    this%words_in_use = 0
  end
  subroutine init_words(this, nbits)
    type(t_bitset), intent(inout) :: this
    integer, intent(in) :: nbits
    if (allocated(this%words)) deallocate(this%words)
    allocate(this%words(0:words_index(nbits - 1)))
    this%words = 0
  end
  type(t_bitset) function newb0() result(res)
    call init_words(res, bits_per_word)
  end
  type(t_bitset) function newb1(nbits) result(res)
    integer, intent(in) :: nbits
    call assert(nbits >= 0, "nbits < 0 at newb1()")
    call init_words(res, nbits)
  end
  type(t_bitset) function newb2(words) result(res)
    integer(8), intent(in) :: words(:)
    allocate(res%words(0:size(words) - 1))
    res%words = words
    res%words_in_use = size(words)
    call check_invariants(res)
  end
  type(t_bitset) function newb3(longs) result(res)
    integer(8), intent(in) :: longs(:)
    integer :: i
    do i = size(longs), 1, -1
      if (longs(i) /= 0) then
        res = newb2(longs(1:i))
        return
      end if
    end do
    res = newb0()
  end
  subroutine ensure_capacity(this, words_required)
    type(t_bitset), intent(inout) :: this
    integer, intent(in) :: words_required
    integer :: request
    integer(8), allocatable :: copy(:)
    if (size(this%words) >= words_required) return
    request = max(2 * size(this%words), words_required)
    allocate(copy(size(this%words)))
    copy = this%words
    deallocate(this%words)
    allocate(this%words(0:request - 1))
    this%words = 0
    this%words(0:size(copy) - 1) = copy
  end
  subroutine expand_to(this, word_index)
    type(t_bitset), intent(inout) :: this
    integer, intent(in) :: word_index
    integer :: words_required
    words_required = word_index + 1
    if (this%words_in_use < words_required) then
      call ensure_capacity(this, words_required)
      this%words_in_use = words_required
    end if
  end
  subroutine check_range(from_index, to_index)
    integer, intent(in) :: from_index, to_index
    call assert(0 <= from_index .and. from_index <= to_index, "At check_range()")
  end
  subroutine flip0(this, bit_index)
    class(t_bitset), intent(inout) :: this
    integer, intent(in) :: bit_index
    integer :: word_index
    call assert(bit_index >= 0, "bit_index < 0 at flip0()")
    word_index = words_index(bit_index)
    call expand_to(this, word_index)
    this%words(word_index) = xor(this%words(word_index), slshift(1_8, bit_index))
    call recalculate_words_in_use(this)
    call check_invariants(this)
  end
  subroutine flip1(this, from_index, to_index)
    class(t_bitset), intent(inout) :: this
    integer, intent(in) :: from_index, to_index
    integer :: start_word_index, end_word_index, idx
    integer(8) :: first_word_mask, last_word_mask
    call check_range(from_index, to_index)
    if (from_index == to_index) return
    start_word_index = words_index(from_index)
    end_word_index = words_index(to_index - 1)
    call expand_to(this, end_word_index)
    first_word_mask = slshift(word_mask, from_index)
    last_word_mask = urshift(word_mask, -to_index)
    if (start_word_index == end_word_index) then
      idx = start_word_index
      this%words(idx) = xor(this%words(idx), and(first_word_mask, last_word_mask))
    else
      idx = start_word_index
      this%words(idx) = xor(this%words(idx), first_word_mask)
      do idx = start_word_index + 1, end_word_index - 1
        this%words(idx) = xor(this%words(idx), word_mask)
      end do
      idx = end_word_index
      this%words(idx) = xor(this%words(idx), last_word_mask)
    end if
    call recalculate_words_in_use(this)
    call check_invariants(this)
  end
  subroutine set0(this, bit_index)
    class(t_bitset), intent(inout) :: this
    integer, intent(in) :: bit_index
    integer :: word_index
    call assert(bit_index >= 0, "bit_index < 0 at set0()")
    word_index = words_index(bit_index)
    call expand_to(this, word_index)
    this%words(word_index) = or(this%words(word_index), slshift(1_8, bit_index))
    call check_invariants(this)
  end
  subroutine clear0(this, bit_index)
    class(t_bitset), intent(inout) :: this
    integer, intent(in) :: bit_index
    integer :: word_index
    call assert(bit_index >= 0, "bit_index < 0 at clear0()")
    word_index = words_index(bit_index)
    if (word_index >= this%words_in_use) return
    this%words(word_index) = and(this%words(word_index), not(slshift(1_8, bit_index)))
    call recalculate_words_in_use(this)
    call check_invariants(this)
  end
  subroutine setval0(this, bit_index, val)
    class(t_bitset), intent(inout) :: this
    integer, intent(in) :: bit_index
    logical, intent(in) :: val
    if (val) then
      call set0(this, bit_index)
    else
      call clear0(this, bit_index)
    end if
  end
  subroutine set1(this, from_index, to_index)
    class(t_bitset), intent(inout) :: this
    integer, intent(in) :: from_index, to_index
    integer :: start_word_index, end_word_index, idx
    integer(8) :: first_word_mask, last_word_mask
    call check_range(from_index, to_index)
    if (from_index == to_index) return
    start_word_index = words_index(from_index)
    end_word_index = words_index(to_index - 1)
    call expand_to(this, end_word_index)
    first_word_mask = slshift(word_mask, from_index)
    last_word_mask = urshift(word_mask, -to_index)
    if (start_word_index == end_word_index) then
      idx = start_word_index
      this%words(idx) = or(this%words(idx), and(first_word_mask, last_word_mask))
    else
      idx = start_word_index
      this%words(idx) = or(this%words(idx), first_word_mask)
      do idx = start_word_index + 1, end_word_index - 1
        this%words(idx) = word_mask
      end do
      idx = end_word_index
      this%words(idx) = or(this%words(idx), last_word_mask)
    end if
    call check_invariants(this)
  end
  subroutine clear1(this, from_index, to_index_)
    class(t_bitset), intent(inout) :: this
    integer, intent(in) :: from_index, to_index_
    integer :: to_index
    integer :: start_word_index, end_word_index, idx
    integer(8) :: first_word_mask, last_word_mask
    to_index = to_index_
    call check_range(from_index, to_index)
    if (from_index == to_index) return
    start_word_index = words_index(from_index)
    if (start_word_index >= this%words_in_use) return
    end_word_index = words_index(to_index - 1)
    if (end_word_index >= this%words_in_use) then
      to_index = length(this)
      end_word_index = this%words_in_use - 1
    end if
    first_word_mask = slshift(word_mask, from_index)
    last_word_mask = urshift(word_mask, -to_index)
    if (start_word_index == end_word_index) then
      idx = start_word_index
      this%words(idx) = and(this%words(idx), not(and(first_word_mask, last_word_mask)))
    else
      idx = start_word_index
      this%words(idx) = and(this%words(idx), not(first_word_mask))
      do idx = start_word_index + 1, end_word_index - 1
        this%words(idx) = 0
      end do
      idx = end_word_index
      this%words(idx) = and(this%words(idx), not(last_word_mask))
    end if
    call recalculate_words_in_use(this)
    call check_invariants(this)
  end
  subroutine setval1(this, from_index, to_index, val)
    class(t_bitset), intent(inout) :: this
    integer, intent(in) :: from_index, to_index
    logical, intent(in) :: val
    if (val) then
      call set1(this, from_index, to_index)
    else
      call clear1(this, from_index, to_index)
    end if
  end
  subroutine clear2(this)
    class(t_bitset), intent(out) :: this
    this%words(0:this%words_in_use - 1) = 0
    this%words_in_use = 0
  end
  logical function get0(this, bit_index) result(res)
    class(t_bitset), intent(in) :: this
    integer, intent(in) :: bit_index
    integer :: word_index
    call assert(bit_index >= 0, "bit_index < 0 at get0()")
    call check_invariants(this)
    word_index = words_index(bit_index)
    if (word_index >= this%words_in_use) then
      res = .false.
      return
    end if
    res = and(this%words(word_index), slshift(1_8, bit_index)) /= 0
  end
  type(t_bitset) function get1(this, from_index, to_index_) result(res)
    class(t_bitset), intent(in) :: this
    integer, intent(in) :: from_index, to_index_
    integer :: to_index, len
    integer :: target_words, source_index, idx
    logical :: word_aligned
    integer(8) :: last_word_mask
    to_index = to_index_
    call check_range(from_index, to_index)
    call check_invariants(this)
    len = length(this)
    if (len <= from_index .or. from_index == to_index) then
      res = newb0()
      return
    end if
    if (to_index > len) to_index = len
    res = newb1(to_index - from_index)
    target_words = words_index(to_index - from_index - 1) + 1
    source_index = words_index(from_index)
    word_aligned = and(from_index, bit_index_mask) == 0
    do idx = 0, target_words - 2
      if (word_aligned) then
        res%words(idx) = this%words(source_index)
      else
        res%words(idx) = or(urshift(this%words(source_index), from_index), slshift(this%words(source_index + 1), -from_index))
      end if
      source_index = source_index + 1
    end do
    last_word_mask = urshift(word_mask, -to_index)
    if (and(to_index - 1, bit_index_mask) < and(from_index, bit_index_mask)) then
      res%words(target_words - 1) = or(urshift(this%words(source_index), from_index), &
        slshift(and(this%words(source_index + 1), last_word_mask), -from_index))
    else
      res%words(target_words - 1) = urshift(and(this%words(source_index), last_word_mask), from_index)
    end if
    res%words_in_use = target_words
    call recalculate_words_in_use(res)
    call check_invariants(res)
  end
  integer function next_set_bit(this, from_index) result(res)
    class(t_bitset), intent(in) :: this
    integer, intent(in) :: from_index
    integer :: u
    integer(8) :: word
    call assert(from_index >= 0, "from_index < 0 at next_set_bit()")
    call check_invariants(this)
    u = words_index(from_index)
    if (u >= this%words_in_use) then
      res = -1
      return
    end if
    word = and(this%words(u), slshift(word_mask, from_index))
    do
      if (word /= 0) then
        res = (u * bits_per_word) + number_of_trailing_zeros(word)
        return
      end if
      u = u + 1
      if (u == this%words_in_use) then
        res = -1
        return
      end if
      word = this%words(u)
    end do
  end
  integer function next_clear_bit(this, from_index) result(res)
    class(t_bitset), intent(in) :: this
    integer, intent(in) :: from_index
    integer :: u
    integer(8) :: word
    call assert(from_index >= 0, "from_index < 0 at next_clear_bit()")
    call check_invariants(this)
    u = words_index(from_index)
    if (u >= this%words_in_use) then
      res = from_index
      return
    end if
    word = and(not(this%words(u)), slshift(word_mask, from_index))
    do
      if (word /= 0) then
        res = (u * bits_per_word) + number_of_trailing_zeros(word)
        return
      end if
      u = u + 1
      if (u == this%words_in_use) then
        res = this%words_in_use * bits_per_word
        return
      end if
      word = not(this%words(u))
    end do
  end
  integer function previous_set_bit(this, from_index) result(res)
    class(t_bitset), intent(in) :: this
    integer, intent(in) :: from_index
    integer :: u
    integer(8) :: word
    if (from_index < 0) then
      call assert(from_index == -1, "from_index < -1 at previous_set_bit()")
      res = -1
      return
    end if
    call check_invariants(this)
    u = words_index(from_index)
    if (u >= this%words_in_use) then
      res = length(this) - 1
      return
    end if
    word = and(this%words(u), urshift(word_mask, -(from_index + 1)))
    do
      if (word /= 0) then
        res = (u + 1) * bits_per_word - 1 - number_of_leading_zeros(word)
        return
      end if
      if (u == 0) then
        res = -1
        return
      end if
      u = u - 1
      word = this%words(u)
    end do
  end
  integer function previous_clear_bit(this, from_index) result(res)
    class(t_bitset), intent(in) :: this
    integer, intent(in) :: from_index
    integer :: u
    integer(8) :: word
    if (from_index < 0) then
      call assert(from_index == -1, "from_index < -1 at previous_clear_bit()")
      res = -1
      return
    end if
    call check_invariants(this)
    u = words_index(from_index)
    if (u >= this%words_in_use) then
      res = from_index
      return
    end if
    word = and(not(this%words(u)), urshift(word_mask, -(from_index + 1)))
    do
      if (word /= 0) then
        res = (u + 1) * bits_per_word - 1 - number_of_leading_zeros(word)
        return
      end if
      if (u == 0) then
        res = -1
        return
      end if
      u = u - 1
      word = not(this%words(u))
    end do
  end
  integer function length(this) result(res)
    class(t_bitset), intent(in) :: this
    integer :: u, n
    u = this%words_in_use
    if (u == 0) then
      res = 0
    else
      n = number_of_leading_zeros(this%words(u - 1))
      res = bits_per_word * (u - 1) + (bits_per_word - n)
    end if
  end
  logical function is_empty(this) result(res)
    class(t_bitset), intent(in) :: this
    res = this%words_in_use == 0
  end
  logical function is_not_empty(this) result(res)
    class(t_bitset), intent(in) :: this
    res = this%words_in_use > 0
  end
  logical function intersects(this, other) result(res)
    class(t_bitset), intent(in) :: this
    type(t_bitset), intent(in) :: other
    integer :: m, i
    m = min(this%words_in_use, other%words_in_use)
    do i = m, 0, -1
      if (and(this%words(i), other%words(i)) /= 0) then
        res = .true.
      end if
    end do
    res = .false.
  end
  integer function cardinality(this) result(res)
    class(t_bitset), intent(in) :: this
    res = sum(popcnt(this%words(0:this%words_in_use - 1)))
  end
  subroutine and0(this, other)
    class(t_bitset), intent(inout) :: this
    type(t_bitset), intent(in) :: other
    integer :: i
    do while (this%words_in_use > other%words_in_use)
      this%words_in_use = this%words_in_use - 1
      this%words(this%words_in_use) = 0
    end do
    do i = 0, this%words_in_use - 1
      this%words(i) = and(this%words(i), other%words(i))
    end do
    call recalculate_words_in_use(this)
    call check_invariants(this)
  end
  subroutine or0(this, other)
    class(t_bitset), intent(inout) :: this
    type(t_bitset), intent(in) :: other
    integer :: u, i
    u = min(this%words_in_use, other%words_in_use)
    do i = 0, u - 1
      this%words(i) = or(this%words(i), other%words(i))
    end do
    if (u < other%words_in_use) then
      call ensure_capacity(this, other%words_in_use)
      this%words_in_use = other%words_in_use
      this%words(u:this%words_in_use - 1) = other%words(u:other%words_in_use - 1)
    end if
    call check_invariants(this)
  end
  subroutine xor0(this, other)
    class(t_bitset), intent(inout) :: this
    type(t_bitset), intent(in) :: other
    integer :: u, i
    u = min(this%words_in_use, other%words_in_use)
    do i = 0, u - 1
      this%words(i) = xor(this%words(i), other%words(i))
    end do
    if (u < other%words_in_use) then
      call ensure_capacity(this, other%words_in_use)
      this%words_in_use = other%words_in_use
      this%words(u:this%words_in_use - 1) = other%words(u:other%words_in_use - 1)
    end if
    call recalculate_words_in_use(this)
    call check_invariants(this)
  end
  subroutine and_not0(this, other)
    class(t_bitset), intent(inout) :: this
    type(t_bitset), intent(in) :: other
    integer :: u, i
    u = min(this%words_in_use, other%words_in_use)
    do i = 0, u - 1
      this%words(i) = and(this%words(i), not(other%words(i)))
    end do
    call recalculate_words_in_use(this)
    call check_invariants(this)
  end
  integer function size0(this) result(res)
    class(t_bitset), intent(in) :: this
    res = size(this%words) * bits_per_word
  end
end module mod_bitset
program balanced_path
  use mod_bitset
  implicit none
  integer :: h, w, a(80, 80) = 0, b(80) = 0, i, j, k
  type(t_bitset) :: dp(80, 80)
  read(*,*) h, w
  do i = 1, h
    read(*,*) a(i, 1:w)
  end do
  do i = 1, h
    read(*,*) b(1:w)
    a(i, 1:w) = abs(a(i, 1:w)-b(1:w))
  end do
  do i = 1, h
    do j = 1, w
      dp(i, j) = bitset()
    end do
  end do
  call dp(1, 1)%set(a(1, 1))
  do i = 1, h
    do j = 1, w
      if (i > 1) then
        do k = 0, 12800
          if (dp(i - 1, j)%get(k)) then
            call dp(i, j)%set(abs(k - a(i, j)))
            call dp(i, j)%set(k + a(i, j))
          end if
        end do
      end if
      if (j > 1) then
        do k = 0, 12800
          if (dp(i, j - 1)%get(k)) then
            call dp(i, j)%set(abs(k - a(i, j)))
            call dp(i, j)%set(k + a(i, j))
          end if
        end do
      end if
    end do
  end do
  do k = 0, 12800
    if (dp(h, w)%get(k)) then
      write(*,'(i0)') k
      stop
    end if
  end do
end program balanced_path