N  = int(input())
S = list(input())
DP = [0]*3
mod = 998244353
v = list('LRU.').index(S[0])
if v==3:
    DP=[1]*3
else:
    DP[v]=1
for s in S[1:]:
    NDP = [0]*3
    if s=='L' or s=='.':
        NDP[0]=(DP[0]+DP[2])%mod
    if s=='R' or s=='.':
        NDP[1]=sum(DP)%mod
    if s=='U' or s=='.':
        NDP[2]=sum(DP)%mod

    DP = NDP
print(sum(DP)%mod)