$510840120140425 = 0
while(A[$510840120140425/W+1,$510840120140425%W+1] == B[$510840120140425/W+1,$510840120140425%W+1])
    $510840120140425 = $510840120140425+1
end
return($510840120140425/W+1,$510840120140425%W+1)