#include <bits/stdc++.h>
using namespace std;

int main() {
  int N, K;
  string S;
  cin >> N >> K >> S;

  constexpr int mod = 998244353;
  int fact[300001], inv[300001], inv_fact[300001];
  fact[0] = inv_fact[0] = 1;
  fact[1] = inv_fact[1] = inv[1] = 1;
  for (int i = 2; i <= 300000; ++i) {
    fact[i] = (long long)i * fact[i-1] % mod;
    inv[i] = (long long)(mod - inv[mod % i]) * (mod / i) % mod;
    inv_fact[i] = (long long)inv[i] * inv_fact[i-1] % mod;
  }

  int cnt{};
  for (int i = 0; i < N; ++i)
    if (S[i] == 'N') {
      if (i == 0)
        ++cnt;
      else if (S[i-1] == 'C')
        --K;
      else
        ++cnt;
    }
  int ans{};
  for (int k = 1; k <= cnt - max(K, 0); ++k) {
    ans += (long long)fact[cnt] * inv_fact[cnt-k] % mod * inv_fact[k] % mod;
    ans %= mod;
  }

  cout << ans << endl;
}