package main

import . "fmt"

func main() {
	var n int
	var s string
	Scan(&n,&s)
	const m=998244353
	var lc,rc,uc int64
	for _,x:=range s {
		switch x {
			case 'L':
			lc,rc,uc=lc+uc,0,0
			case 'R':
			lc,rc,uc=0,lc+rc+uc,0
			case 'U':
			lc,rc,uc=0,0,lc+rc+uc
			case '.':
			lc,rc,uc=lc+uc,lc+rc+uc,lc+rc+uc
		}
		lc,rc,uc=lc%m,rc%m,uc%m
	}
	Println((lc+rc+uc)%m)
}