Search for 404

Om has a string $S$ consisting of characters $*$, $4$, and $0$ only. - The character $*$ can be replaced by either $4$ or $0$. Om wants to count the total number of [subsequences](https://en.wikipedia.org/wiki/Subsequence) of $404$ present in all the possible strings generated after replacing $*$. As the number can be huge, you must output the number modulo $10^{9}+7$. For example, if the give