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#9479. And DNA

統計

给定两个整数 $N$ 和 $M$,计算长度为 $N$ 的序列 $A = (A_1, A_2, \dots, A_N)$ 的数量,其中每个 $A_i$ 都是 $0$ 到 $M$ 之间的整数(包含 $0$ 和 $M$),且满足以下条件:

  • 对于所有 $i = 1, 2, \dots, N$,满足 $A_i + (A_{i-1} \& A_{i+1}) = M$,其中 $A_0 := A_N$ 且 $A_{N+1} := A_1$。这里 $\&$ 表示按位与运算。

输出答案对 $998244353$ 取模的结果。

输入格式

输入通过标准输入给出,格式如下:

$N \ M$

  • $3 \le N \le 10^9$
  • $0 \le M \le 10^9$
  • 所有输入值均为整数。

输出格式

在一行中输出答案。

样例

样例输入 1

3 2

样例输出 1

4

样例输入 2

3 0

样例输出 2

1

样例输入 3

100 100

样例输出 3

343406454

说明

在第一个样例中,共有 4 个序列满足条件:$(0, 2, 2), (2, 0, 2), (2, 2, 0), (1, 1, 1)$。 在第二个样例中,唯一满足条件的序列是 $(0, 0, 0)$。

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