RT。

如果不加（$k$ 在long long范围内），那么可以 Hack:

1. https://www.luogu.com.cn/blog/milkfilling/solution-p3373
2. https://www.luogu.com.cn/blog/lhr/solution-p3373
3. https://www.luogu.com.cn/blog/chuanxinbanben/solution-p3373
4. https://www.luogu.com.cn/blog/ctq1999/solution-p3373
5. https://www.luogu.com.cn/blog/running-coder/solution-p3373
6. https://www.luogu.com.cn/blog/logwzc/solution-p3373
7. https://www.luogu.com.cn/blog/ahaha254/solution-p3373
8. https://www.luogu.com.cn/blog/firstfan/segment-tree
9. https://www.luogu.com.cn/blog/zy-E/p3373-mu-ban-xian-duan-shu-2-post
10. https://www.luogu.com.cn/blog/ylx/solution-p3373
11. https://www.luogu.com.cn/blog/Lskkkno1/yong-ju-zhen-biao-shi-bian-hua-xian-duan-shu-wei-hu-ju-zhen
12. https://www.luogu.com.cn/blog/2005czq/solution-p3373
13. https://www.luogu.com.cn/blog/whitenight/solution-p3373
14. https://ultramanz.blog.luogu.org/solution-p3373
15. https://www.luogu.com.cn/blog/OliverHeldensBlog/xian-duan-shu-2-post
16. https://www.luogu.com.cn/blog/ksydom/xian-duan-shu-2-ji-shi-shi-zong-ti-xie
17. https://www.luogu.com.cn/blog/lxzsyingyingying/solution-p3373
18. https://www.luogu.com.cn/blog/user48611/solution-p3373
19. https://www.luogu.com.cn/blog/user28939/solution-p3373
20. https://www.luogu.com.cn/blog/2721402616cgp/solution-p3373
21. https://www.luogu.com.cn/blog/PBCWZCC-BLOG/solution-p3373
22. https://www.luogu.com.cn/blog/xky-666/solution-p3373
23. https://www.luogu.com.cn/blog/TheDawn/solution-p3373
24. https://www.luogu.com.cn/blog/user54636/solution-p3373
25. https://www.luogu.com.cn/blog/user39907/solution-p3373
26. https://www.luogu.com.cn/blog/user38945/solution-p3373
27. https://www.luogu.com.cn/blog/yhzq/solution-p3373
28. https://www.luogu.com.cn/blog/user14738/solution-p3373
29. https://www.luogu.com.cn/blog/litble-blog/solution-p3373
30. https://www.luogu.com.cn/blog/user23388/solution-p3373
31. https://www.luogu.com.cn/blog/kevinshuai/solution-p3373
32. https://www.luogu.com.cn/blog/pupuvovovovo/solution-p3373（将函数 $\operatorname{ch_a}$ 中的 $\operatorname{ch_t}$ 改成 $\operatorname{ch_a}$ 后评测）
33. https://www.luogu.com.cn/blog/user22108/solution-p3373
34. https://www.luogu.com.cn/blog/user28023/solution-p3373
35. https://www.luogu.com.cn/blog/lyfzxl/solution-p3373
36. https://www.luogu.com.cn/blog/chenxinyang2006/solution-p3373
37. https://www.luogu.com.cn/blog/SYF--WZR--love/solution-p3373（CE，修改后评测）
38. https://www.luogu.com.cn/blog/EricWay1024/solution-p3373
39. https://www.luogu.com.cn/blog/Agumon/solution-p3373
40. https://www.luogu.com.cn/blog/ShadowassIIXVIIIIV/solution-p3373
41. https://www.luogu.com.cn/blog/user17326/solution-p3373
42. https://www.luogu.com.cn/blog/fylsea/solution-p3373（CE，修改后评测）
43. https://www.luogu.com.cn/blog/user27276/solution-p3373

通过 Hack:

1. https://www.luogu.com.cn/blog/user36788/solution-p337
2. https://www.luogu.com.cn/blog/shrshrshr/solution-p3373（链接访问失效，实为第 3 页第 7 篇）
3. https://www.luogu.com.cn/blog/user70545/solution-p3373（int main没写int，帮忙加了）
4. https://www.luogu.com.cn/blog/user54721/solution-p3373
5. https://www.luogu.com.cn/blog/user27138/solution-p3373
6. https://www.luogu.com.cn/blog/2065037421deadgun/p3373-mu-ban-xian-duan-shu-2-post

未放完整代码：

1. https://www.luogu.com.cn/blog/ksydom/xian-duan-shu-2-ji-shi-shi-zong-ti-xie
2. https://www.luogu.com.cn/blog/hkr04/solution-p3373
3. https://www.luogu.com.cn/blog/cscy/solution-p3373
4. https://www.luogu.com.cn/blog/surf/segment-fhqtreap

萌新第一次进行 Hack（其实是建议），可能有错误，勿喷！

另：某篇题解似乎漏加了，懒得找了