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