while($0 < H * W)
  $1 = $0 / W + 1
  $2 = $0 % W + 1
  $3 = A[$1,$2] - B[$1,$2]
  $4 = $4 + $3
  $11 = $11 + $3 * $1
  $12 = $12 + $3 * $2
  $0 = $0 + 1
end
$11 = $11 / $4
$12 = $12 / $4
return($11, $12)