Thanks for all your constructive and nice advice in advance ^)^
I will state my problem once again in more details ...all the problems we discussing is about digit and independent of letter . different letter is just stand for different digit...
Question : ABC-ABD-ABE is a 9 bit numeric string( A B C D E are different dgit, C D E must be sequential and sort ascending) , just like 124125126 , 253254255 ,192193194 ,384385386 ,781782783 and so on .
Many thanks and best regards,