#TLE解法です。
import math
MOD = 998244353
N,K = map(int,input().split())
DP = [[0]*(N+2) for i in range(N+1)]
DP[0][0] = 1
for i in range(N):
    for j in range(N+1):
        DP[i+1][j] = (DP[i+1][j] + DP[i][j])%MOD
        DP[i+1][j+1] = (DP[i+1][j+1] + DP[i][j])%MOD
S = input()
tmp = 0
hima = 0
for i in range(N):
    if i != 0:
        if S[i] == "N" and S[i-1] != "C":
            tmp += 1
    else:
        if S[i] == "N":
            tmp += 1
    if S[i] == "N":
        hima += 1
ans = 0
for i in range(1,hima-K+1):
    ans += DP[tmp][i]
    ans %= MOD
print(ans)