Comments
 On chokudai → AtCoder Beginner Contest 182 Announcement, 4 years ago 0 How to solve problem F?
 On dario2994 → Codeforces Global Round 11, 4 years ago -6 Hope strong pretests.Come Up~
 On Wind_Eagle → Codeforces Round #672 (Div. 2), 4 years ago +3 I like this kind of contest with strong pretests. For problem D, enumerate the ending points of all values, and then count the number of new values $a$ each time, and the number of values that are still ending before $b$. The added contribution of the answer is: COMB(a + b, k) — COMB(b, k).
 On Wind_Eagle → Codeforces Round #672 (Div. 2), 4 years ago 0 If a[i] is greater than a[i-1] and a[i+1], add a[i] to the answer. If a[i] is less than a[i-1] and a[i+1], subtract a[i] from the answer. And let a[0]=a[n+1]=0. Change the contribution of up to 6 positions per exchange. Complexity: O(n).
 On awoo → Educational Codeforces Round 95 [Rated for Div. 2], 4 years ago -8 Does anyone check the correctness of the problem A??? Bad experience!
 On gyh20 → Codeforces Round #670 (Div. 2) Editorial, 4 years ago 0 Can problem D find legal arrays of $b$ and $c$? upd:Oh, yes, it can be done.
 On majk → Good Bye 2018, 5 years ago +5 Problem D. I don't sure it's correctness. a[n]=n*(a[n-1]-1) starting with a[1]=3. ans = n!*(n-2) + a[n-2]
 On MikeMirzayanov → New Year Gifts 2019!, 5 years ago 0 Happy new year! I finally experienced the gray rank!Wowo! Try to experience all kinds of color in Codeforces.
 On awoo → Educational Codeforces Round 49 [Rated for Div. 2], 6 years ago +1 The internet of machine room is out of service, sadly I have to use my wifi to play codeforces....
 On MikeMirzayanov → Rule about third-party code is changing, 6 years ago -31 I dont know the rules of CF.And the other account is mine too.I submit my code on my account and i submit it with this account. Whatever,i am sorry for this thing happened.