|시간 제한||메모리 제한||제출||정답||맞은 사람||정답 비율|
|1 초||256 MB||2||1||1||100.000%|
There is an $H \times W$ grid. Let $(i,\ j)$ be the cell at the intersection of the $i$-th row ($0 \leq i \leq H-1$) and the $j$-th column ($0 \leq j \leq W-1$). Initially, there is an eel at the cell $(0,\ 0)$. The eel repeats the following process.
Count the number of ways to paint all cells and end the process at the cell $(0,\ 0)$, modulo $10^9+7$. Two ways are considered distinct if the path traveled by the eel are distinct.
Print the answer modulo $10^9+7$.
The following picture shows the two ways in Sample 1: