#include <bits/stdc++.h>
#include <atcoder/all>
using namespace std;
using namespace atcoder;
using ll = long long;
using ld = long double;
using mint = modint998244353;

const int MAX = 505050;
const int MOD = 998244353;

long long fac[MAX], finv[MAX], inv[MAX];

void COMinit() {
    fac[0] = fac[1] = 1;
    finv[0] = finv[1] = 1;
    inv[1] = 1;
    for (int i = 2; i < MAX; i++){
        fac[i] = fac[i - 1] * i % MOD;
        inv[i] = MOD - inv[MOD%i] * (MOD / i) % MOD;
        finv[i] = finv[i - 1] * inv[i] % MOD;
    }
}

long long COM(int n, int k){
    if (n < k) return 0;
    if (n < 0 || k < 0) return 0;
    return fac[n] * (finv[k] * finv[n - k] % MOD) % MOD;
}

int main() {
  COMinit();
  int n, k; cin >> n >> k;
  string s; cin >> s;
  int c = 0, d = 0;
  for (int i = 0; i < n; i++) {
    if (s[i] == 'N') {
      if (i != 0 && s[i - 1] == 'C') d++;
      else c++;
    }
  }
  if (c - k + d <= 0) {
    cout << 0 << endl;
    return 0;
  }
  ll ans = 0;
  for (int i = 0; i < c - k + d; i++) ans = (ans + COM(c, i + 1)) % MOD;
  cout << ans << endl;
  return 0;
}