1.sum局部变量没初始化；
2.输入1e9时i会爆int
by Z_X_D_ @ 2023-09-27 11:26:50
@[Z_X_D_](/user/371309) 俺没听懂555
by dead000 @ 2023-09-27 12:16:46
@[Z_X_D_](/user/371309) 懂啦懂啦，谢谢佬
by dead000 @ 2023-09-27 12:21:10