#pragma GCC target("avx2")
#pragma GCC optimize("O3")
#pragma GCC optimize("unroll-loops")
#include <bits/stdc++.h>
#include<atcoder/modint>
using namespace atcoder;
using namespace std;
#define rep(i, n) for (int i = 0; i < (int) (n); i++)
using mint = modint998244353;
vector<mint> fact, factinv, inv;
const int mod = 998244353;
void prenCkModp(int n) {
    fact.resize(n + 5);
    factinv.resize(n + 5);
    inv.resize(n + 5);
    fact[0] = fact[1] = 1;
    factinv[0] = factinv[1] = 1;
    inv[1] = 1;
    for (int i = 2; i < n + 5; i++) {
        fact[i] = (fact[i - 1] * i);
        inv[i] = (mod - ((inv[mod % i] * (mod / i))));
        factinv[i] = (factinv[i - 1] * inv[i]);
    }
}
mint nCk(int n, int k) {
    if (n < k || k < 0) return 0;
    return (fact[n] * ((factinv[k] * factinv[n - k])));
}

int main() {

    cin.tie(nullptr);
    ios::sync_with_stdio(false);

    int N,K;
    string S;
    cin>>N>>K>>S;
    
    int cnt=0,nnt=0;
    rep(i,N){
        if(S[i]=='N'){
            if(i==0||S[i-1]!='C')cnt++;
            nnt++;
        }
    }
    mint an=0;
    prenCkModp(cnt);
    for(int i=1;i<=cnt&&nnt-i>=K;i++){
        an+=nCk(cnt,i);
    }
    cout<<an.val()<<endl;


}