#include <bits/stdc++.h>
#define rep(i,n) for(ll i = 0; i < n; i++) //[0,n)
#define srep(i,a,b) for(ll i = a; i < b; i++) //[a,b)
#define all(A) (A).begin(),(A).end()
#define pmt(A) next_permutation(all(A))
using namespace std;
using ll = long long;
using ull = unsigned long long;
using P = pair<ll,ll>;
using pq = priority_queue<P,vector<P>,greater<P>>;
ll inf = 1LL<<60;
int iinf = (int)1e9+1;
int mod9 = 998244353;
int mod1 = 1000000007;
struct Edge { int to; int cost; int from; };
bool compe(const Edge &e,const Edge &e2){ return e.cost < e2.cost; }
using Graph = vector<vector<ll>>;
using SGraph = vector<set<ll>>;
template <typename T>
int siz(T& a){return (int)a.size();}
ll squa(ll a){ return a*a; }
ll ceil(ll a,ll b){ return (a+b-1)/b; }

ll const MAX = 1010101;
ll fac[MAX],finv[MAX],inv[MAX];
void Cinit(ll mod){
	fac[0] = fac[1] = 1;
	finv[0] = finv[1] = 1;
	inv[1] = 1;
	srep(i,2,MAX){
		fac[i] = fac[i-1]*i%mod;
		inv[i] = mod-inv[mod%i]*(mod/i)%mod;
		finv[i] = finv[i-1]*inv[i]%mod;
	}
}

ll nCr(int n,int k,ll mod){
	if(n < k || (n < 0 || k < 0)) return 0;
	return fac[n]*(finv[k]*finv[n-k]%mod)%mod;
}

int main(void){
	Cinit(mod9);

	int N,K; cin >> N >> K;
	string S; cin >> S;

	int cnt = 0,Ncnt = 0;
	rep(i,N){
		if(i+1 < N && S[i] == 'C' && S[i+1] == 'N') cnt++;
		if(S[i] == 'N') Ncnt++;
	}
	K -= cnt;
	Ncnt -= cnt;

	ll ans = 0;
	rep(i,max(Ncnt-K,0)) (ans += nCr(Ncnt,i+1,mod9)) %= mod9;
	cout << ans;
}