$0 = 0
$1 = 0
$2 = 0

while (A[$1 + 1, $2 + 1] == B[$1 + 1, $2 + 1])
  $0 = $0 + 1
  $1 = $0 / W
  $2 = $0 % W
end

return ($1 + 1, $2 + 1)