N = int(input())
S = input()
dp = [[0,0,0] for _ in range(N)]
mod = 998244353
if S[0] == "L":
    dp[0][0] = 1
elif S[0] == "U":
    dp[0][1] = 1
elif S[0] == "R":
    dp[0][2] = "1"
else:
    if len(S) == 1:
        dp[0][0] = 3
    else:
        if S[1] == "L":
            dp[0][0],dp[0][1] = 1,1
        else:
            dp[0] = [1,1,1]

for a in range(1,N-1):
    X = [0,0,0]
    P = dp[a-1]
    if S[a] == ".":
        if S[a+1] == "L":
            X[0] = P[0] + P[1]
            X[1] = P[0] + P[1] + P[2]
        else:
            X[0] = P[0] + P[1]
            X[1] = P[1] + P[2] + P[0]
            X[2] = P[1] + P[2] + P[0]
        for b in range(3):
            X[b] %= mod
    elif S[a] == "L":
        X[0] = P[1] + P[0]
        X[0] %= mod
    elif S[a] == "U":
        X[1] = P[1] + P[2] + P[0]
        X[1] %= mod 
    elif S[a] == "R":
        if S[a+1] == "L":
            pass
        else:
            X[2] = P[1] + P[2] + P[0]
            X[2] %= mod
    dp[a] = X

if len(S) >= 2:
    X = [0,0,0]
    P = dp[N-2]
    if S[N-1] == ".":
        X[0] = P[1] + P[0]
        X[1] = P[1] + P[2] + P[0]
        X[2] = P[1] + P[2] + P[0]
    elif S[N-1] == "L":
        X[0] = P[1] + P[0]
    else:
        X[1] = P[1] + P[2] + P[0]
    for b in range(3):
        X[b] %= mod
    dp[N-1] = X
print(sum(dp[N-1])%mod)