If the order is not important, I would sort all Lists (Collections).
This is an easy problem to solve. You have one multiset (collection 1) (it is a "multiset" because the same element can occur multiple times), and then a number of other multisets (collections 2..N), and you want to find a minimum-size subset of collection 1 that does not occur in any of the other collections (2..N).
I cant really gove you an answer,but what I can give you is a way to a solution, that is you have to find the anglde that you relate to or peaks your interest. A good paper is one that people get drawn into because it reaches them ln some way.As for me WW11 to me, I think of the holocaust and the effect it had on the survivors, their families and those who stood by and did nothing until it was too late.