#include <bits/stdc++.h>
#define rep(i,n) for(int i = 0; i < n; i++) //[0,n)
#define srep(i,a,b) for(int i = a; i < b; i++) //[a,b)
#define all(A) (A).begin(),(A).end()
#define rall(A) (A).rbegin(),(A).rend()
#define pmt(A) next_permutation(A)
using namespace std;
using ll = long long;
using ull = unsigned long long;
using P = pair<ll,ll>;
using pq = priority_queue<ll,vector<ll>>;
const ll inf = 8e18;
const int iinf = (int)1e9;
const int mod9 = 998244353;
const int mod1 = 1000000007;
struct Edge {
    int to;
    ll cost;
    int from;
};
bool compe(const Edge &e,const Edge &e2){ return e.cost < e2.cost; }
using Graph = vector<vector<int>>;
using EGraph = vector<Edge>;
using SGraph = vector<set<ll>>;
template <typename T>
int siz(T& a){ return (int)a.size(); }
double squa(double x){ return 1.0*x*x; }
double pi = acos(-1);
using namespace std;

ll const MAX = 303030;
ll const MOD = mod9;
ll fac[MAX],finv[MAX],inv[MAX];
void Cinit(){
	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){
	if(n < k || (n < 0 || k < 0)) return 0;
	return fac[n]*(finv[k]*finv[n-k]%MOD)%MOD;
}

int main(){
    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;

    Cinit();
    ll ans = 0;
    rep(i,ncnt-k) (ans += nCr(ncnt,i+1)) %= mod9;

    cout << ans << endl;
}