N,K = map(int,input().split())
S = input()
MOD = 998244353
Candidate_Day = 0 #予定を入れても良い日
for i in range(N):
    if i != 0:
        if S[i] == "N" and S[i-1] != "C":
            Candidate_Day += 1
    else:
        if S[i] == "N":
            Candidate_Day += 1
ans = 0
tmp = 1
for i in range(1,S.count("N")-K+1):
    if Candidate_Day < i:
        break
    tmp *= (Candidate_Day-i+1)
    tmp *= pow(i,-1,MOD)
    tmp %= MOD
    ans += tmp
    ans %= MOD
print(ans)