N=int(input())
S=input().strip()
MOD=998244353

if "RL" in S:
    print(0)
    exit()

dic = {"L":0, "R":1, "U":2, ".":3}

dp = [[0]*3 for _ in range(3)]

s0,s1 = map(lambda x:dic[x], S[:2])
for i in range(3):
    if not (s0==i or s0==3):continue
    for j in range(3):
        if not (s1==j or s1==3):continue
        dp[j][i] = 1
dp[0][1] = 0 # 禁止

for s in S[2:]:
    s = dic[s]
    dp2 = [[0]*3 for _ in range(3)]
    if s < 3:
        for i in range(3):
            dp2[s][i] = sum(dp[i])%MOD
    else:
        for i in range(3):
            for j in range(3):
                for k in range(3):
                    dp2[k][j] += dp[j][i]
                    dp2[k][j] %= MOD
    dp2[0][1] = 0 # 禁止
    dp = dp2

print(sum(sum(d) for d in dp)%MOD)