n = int(input())
s = input()

MOD = 998244353

# dp = [0,0,0]
#      [L,R,U]
if s[0] == ".":
    dp = [1,1,1]
elif s[0] == "L":
    dp = [1,0,0]
elif s[0] == "R":
    dp = [0,1,0]
else:
    dp = [0,0,1]

for i in range(1, n):
    c = s[i]
    ndp = [0,0,0]

    if c == "L":
        ndp[0] += dp[0]
        ndp[0] += dp[2]
        ndp[0] %= MOD
    elif c == "R":
        ndp[1] += sum(dp)
        ndp[1] %= MOD
    elif c == "U":
        ndp[2] += sum(dp)
        ndp[2] %= MOD
    
    else:
        ndp[0] += dp[0]
        ndp[0] += dp[2]
        ndp[0] %= MOD
        ndp[1] += sum(dp)
        ndp[1] %= MOD
        ndp[2] += sum(dp)
        ndp[2] %= MOD
    
    dp = ndp

ans = sum(dp) % MOD

print(ans)