四道大水题

@misc{pu2019oiicpcotherproblemsmockcontest20190307,
  author = {Pu, Fanyi},
  title  = {四道大水题},
  year   = {2019},
  month  = {3},
  url    = {https://pufanyi.com/blog/oi-icpc/other-problems/mock-contest-20190307}
}