n = int(input())
s = input()
mod = 998244353

# dp[i][j]: s[i - 1]が状態jの時の組み合わせ数
dp = [[0] * 3 for _ in range(n)]
c = s[0]
if c == ".":
    dp[0] = [1] * 3
else:
    dp[0]["LRU".index(c)] = 1
for i in range(1, n):
    c = s[i]
    if c in ".L":
        dp[i][0] = dp[i - 1][0] + dp[i - 1][2]
    if c in ".R":
        dp[i][1] = sum(dp[i - 1])
    if c in ".U":
        dp[i][2] = sum(dp[i - 1])
    for j in range(3):
        dp[i][j] %= mod

ans = sum(dp[n - 1]) % mod
print(ans)