N=int(input())
S=input()
Mod=998244353

dp=[0]*3
dp[0]=1

for i in S:
    ndp=[0]*3
    if i=='L' or i=='.':
        ndp[0]+=dp[0]+dp[1]
    if i=='U' or i=='.':
        ndp[1]+=sum(dp)
    if i=='R' or i=='.':
        ndp[2]+=sum(dp)
    for j in range(3):
        ndp[j]%=Mod
    dp=ndp

s=sum(dp)
print(s%Mod)