it take longer than usual.
i change lot of macro input and retry again and again.
keep find wrong answer, like do not check the small character.
in part 2, forget to check small character more than 2. etc...Workflow:
for input, split start point and other. (which include end point)
transpose them, and keep the original relation. (to get the opposite link later.)
*put ID for easier reference later.
Join first to get all the possible entry.
verify the new chain, whether is small and count is 1.
verify whether is "-end"
verify again the count >2 whether are only have 1 small link appear twice.