Torus Loop

There is a grid of $H$ rows and $W$ columns. The rows are numbered $0,1,\ldots,H-1$ from top to bottom, and the columns are numbered $0,1,\ldots,W-1$ from left to right. Let $(i,j)$ denote the cell at row $i$ and column $j$. You are given $H$ strings $S_0, S_1, \ldots, S_{H-1}$, each of which is of length $W$ and consists of `A` and `B`. In each cell, one of the following two types of tiles is placed. Let $S_{ij}$ denote the $(j+1)$\-th character $(0 \le j \le W-1)$ of the string $S_i$. The type of tile placed in cell $(i,j)$ is $S_{ij}$. * Type A: A single line segment is drawn on the tile’s surface, connecting the midpoints of two adjacent edges.  * Type B: A single line segment is drawn on the tile’s surface, connecting the midpoints of two opposite edges.  These tiles can be freely rotated. When focusing only on the pattern formed by the line segments, there are four ways to rotate a Type-A tile and two ways to rotate a Type-B tile. Therefore, if we distinguish placements only by the pattern of line segments, the number of ways to place the tiles is $4^a \times 2^b$, where $a$ is the number of Type-A tiles and $b$ is the number of Type-B tiles. Among these ways, print the number, modulo $998244353$, of ways such that the line segments on the tiles have no dead ends when viewing the grid as a torus. Here, "the line segments on the tiles have no dead ends when viewing the grid as a torus" if and only if the following two conditions are satisfied for every cell $(i,j)$: * Both of the following exist, or neither of the following exists: * the line segment drawn in the cell $(i,j)$, whose endpoint is the midpoint of the right edge of the cell $(i,j)$ * the line segment drawn in the cell $(i,(j+1)\bmod W)$, whose endpoint is the midpoint of the left edge of the cell $(i,(j+1)\bmod W)$ * Both of the following exist, or neither of the following exists: * the line segment drawn in the cell $(i,j)$, whose endpoint is the midpoint of the bottom edge of the cell $(i,j)$ * the line segment drawn in the cell $((i+1)\bmod H,j)$, whose endpoint is the midpoint of the top edge of the cell $((i+1)\bmod H,j)$ For example, the following placement satisfies the condition:  The following placement does not satisfy the condition. Specifically, while there is no line segment whose endpoint is the midpoint of the right edge of the tile in cell $(0,2)$, there is a line segment whose endpoint is the midpoint of the left edge of the tile in cell $(0,0)$, so the condition is not satisfied.  You are given $T$ test cases; solve each of them. ## Constraints * $1 \le T \le 10^5$ * $2 \le H,W$ * $HW\leq 10^6$ * $S_i\,(0\le i\le H-1)$ are length-$W$ strings consisting of `A` and `B`. * The sum of $H W$ over all test cases is at most $10^6$. * $T$, $H$, and $W$ are integers. ## Input The input is given from Standard Input in the following format: $T$ $case_1$ $case_2$ $\vdots$ $case_T$ Each case is given in the following format: $H$ $W$ $S_0$ $S_1$ $\vdots$ $S_{H-1}$ [samples]