This problem is in Contest(s) below:
Contest 1318:2022秋季C++入门10
Contest 1351:2023寒假C++编程基础集训5
Contest 1392:2023春季C++编程基础训练5
Contest 1792:2025CYX暑期编程训练9
Contest 1559:23秋季C++基础15