Are you allowed to brute force it?

argee a day ago | parent | next [-]

That's how you do it right? It's a BFS with 4 being the max depth, and you print whatever numbers in the problem set which you didn't find.

	▲	twoodfin 16 hours ago \| parent [-]
		Given the problems ITA solved, thinking about the question that way makes perfect sense.

dooglius a day ago | parent | prev [-]

Figuring that out is presumably part of the interview (and would depend on N)