let s say I have two lists:
a = list(1,2,3)
b = list(4,5,6)
因此,我可以有9位名单成员:
(1,4)
(1,5)
(1,6)
(2,4)
(2,5)
(2,6)
(3,4)
(3,5)
(3,6)
Now, given two list members like above, can I find out the pair s index? Like (1,4) from above would be the 1st pair.