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