第九届中国大学生程序设计竞赛（秦皇岛）-（CCPC2023-Qinhuangdao）

F - 质数之谜

https://cpc.csgrandeur.cn/csgoj/problemset/problem?pid=1229

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Codeforces Round 315 (Div. 1)

A. Primes or Palindromes?

https://codeforces.com/contest/568/problem/A

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Denso Create Programming Contest 2022 Winter(AtCoder Beginner Contest 280)

D - Factorial and Multiple

https://atcoder.jp/contests/abc280/tasks/abc280_d

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Educational Codeforces Round 138 (Rated for Div. 2)

D. Counting Arrays

https://codeforces.com/contest/1749/problem/D

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