Problem Statement
There are $n$ squares arranged in a row. Each square has a left- or right-pointing footprint or a hole. The initial state of each square is described by a string $s$ consisting of ., <, >. If the $i$-th character of $s$ is ., the $i$-th square from the left has a hole; if that character is <, that square has a left-pointing footprint; if that character is >, that square has a right-pointing footprint.
Snuke, the cat, will repeat the following procedure until there is no more square with a hole.
- Step
$1$: Choose one square with a hole randomly with equal probability. - Step
$2$: Fill the hole in the chosen square, stand there, and face to the left or right randomly with equal probability. - Step
$3$: Keep walking in the direction Snuke is facing until he steps on a square with a hole or exits the row of squares.
Here, the choices of squares and directions are independent of each other.
When Snuke walks on a square (without a hole), that square gets a footprint in the direction he walks in. If the square already has a footprint, it gets erased and replaced by a new one. For example, in the situation >.<><.><, if Snuke chooses the $6$-th square from the left and faces to the left, the $6$-th, $5$-th, $4$-th, $3$-rd squares get left-pointing footprints: >.<<<<><.
Find the expected value of the number of left-pointing footprints when Snuke finishes the procedures, modulo $998244353$.
Note
When the sought expected value is represented as an irreducible fraction $p/q$, there uniquely exists an integer $r$ such that $rq\equiv p ~(\text{mod } 998244353)$ and $0 \leq r \lt 998244353$ under the Constraints of this problem. This $r$ is the value to be found.
Constraints
$1 \leq n \leq 10^5$$s$is a string of length$n$consisting of.,<,>.$s$contains at least one..
Input
Input is given from Standard Input in the following format:
n
s
Output
Print the expected value of the number of left-pointing footprints, modulo $998244353$.
样例
5
><.<<
3
20
>.>.<>.<<.<>.<..<>><
848117770
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