1.Take first word from first list
2. Check in all lists if it is absent, or always first.
3.If you find some word earlier, take it instead and check again.
4.When you finish with all lists put it in result and continue with next word.
5.Used words can be deleted from lists, or filtered based on result list.
1.Let's assume list B is the first one. 'second' is our first word.
2.It is absent in A - ok.
3.In ะก it is not the first. Let's take first word here ('first') and begin from the beginning.
4.Finally 'first' is selected. Let's put it to result and continue with next word.
5.Remove 'first' from all lists, or bypass when meet members of result.
When you change word in step 3, make some kind of temporary stack of words for avoiding recursion. Or use some increment and not go higher than some N (maybe it is the total number of words? Or even only the number of lists)