Hello, I hope all of you enjoyed my contest!

**[Behind story of A]**

- There is a successful hack for A. I am really surprised.
- My code: https://codeforces.com/contest/1228/submission/61578842

**[Behind story of B]**

- There is no behind story.
- My code: https://codeforces.com/contest/1228/submission/61578841

**[Behind story of C]**

- Initial version of C statement consists of tons of mathematical formula. CF team and testers requested me to reduce amount of mathematical formula.
- This problem was added before a week to the round. If there was no such C, the balance would be bad.
- Thanks for dorijanlendvaj , he improved test data for C a lot!
- My code: https://codeforces.com/contest/1228/submission/61578856

**[Behind story of D]**

- Same as C, I wrote tons of mathematical formula in D. After CF team's request, I reduced the amount of formula.
- This is my personal favorite problem among ABCDEF.
- My code: https://codeforces.com/contest/1228/submission/61578861

**[Behind story of E]**

- MikeMirzayanov changed the name of problem before 10~20 minutes to the contest. It was "Minimum One" before.
- This problem was the easiest to prepare data. Just pure random and $$$k=1$$$ is strong enough.
- I managed to create $$$O(n^3)$$$ pypy3 solution for E in 1 second lol.
- Thanks tfg for providing $$$O(n \log n)$$$ solution.
- My code: https://codeforces.com/contest/1228/submission/61578868

**[Behind story of F]**

- This problem was the hardest to prepare data. We considered more than 10 types of trees to block various kind of WA solutions.
- I intended top-down error-toleration based case handling approach for this contest, but seems other approaches are also ok.
- Also thanks for dorijanlendvaj here, he is real MVP tester.
- My code: https://codeforces.com/contest/1228/submission/61578884

**[Behind story of G (removed problem)]**

- Nobody(including red testers) solved this problem for a week. This problem is saved as spare problem for another Div.1 contest.
- I love this beautiful problem than any other problems I ever made.

Thanks in advance!