题目来源

• A: XXI Open Cup named after E.V. Pankratiev. Grand Prix of Korea, Problem C
  • https://qoj.ac/contest/776/problem/3301
• B: Petrozavodsk Winter 2022. Day 7. Gennady Korotkevich Contest 6, Problem I
  • 随后被用在了 XXII Open Cup named after E.V. Pankratiev, Grand Prix of Gomel
  • https://qoj.ac/contest/825/problem/2624
• C: RuCode 2020 Division A+B Championship Round, Problem I
  • 随后被用在了 XX Open Cup named after E.V. Pankratiev, Grand Prix of Moscow, Problem I
  • https://qoj.ac/contest/923/problem/4219