1. 记得开 ```long long```。
2. 运算过程中乘积可能会爆 ```int```，记得先转 ```long long```。
by Dfkuaid @ 2021-03-22 20:38:59
@[Dfkuaid](/user/162191) 全部开longlong就过了！
by Guxue @ 2021-04-26 14:30:10