Correct answer: The number of $ dp $
Report problem solving:
We are beginning to see some sense novel duck, think carefully discovery was a board duck ,,,
Consider setting $ f_ {i} $ $ = indicates the number of $ I $ J $ the sum [j]
Consider the daily $ dfs $ chant, consider what $ QwQ $ variables to be set up
$ Pos $ and $ lim $ I do not want to talk about a duck ,,, then record a $ len $ 1 represents the actual number of $ num $ 1 indicates the number of goals, and then finished it lie ,,,?
Finally, the answer is $ \ prod i ^ {f_ {i}} $ this too obviously do not want to talk about the $ kk $
No code, $ over $