MOD = 998244353

N, K = map(int, input().split())
S = ['P'] + list(input())

if K > S.count('N'):
    print(0)
    exit()

facts = [1]
inv_facts = [1]

for i in range(1, N):
    facts.append(facts[i-1] * i % MOD)
    inv_facts.append(inv_facts[i-1] * pow(i, MOD-2, MOD) % MOD)

def comb(n, r):
    return facts[n] * inv_facts[n-r] * inv_facts[r] % MOD

max_plan = S.count('N') - K

cnt = 0

for i in range(1, N+1):
    if S[i] == 'N' and S[i-1] != 'C':
        cnt += 1

print(sum(comb(cnt, i) for i in range(1, min(max_plan, cnt) + 1)) % MOD)