#define _USE_MATH_DEFINES
#include <iostream>
#include <string>
#include <algorithm>
#include <vector>
#include <queue>
#include <math.h>
#include <cmath>
#include <stack>
#include <map>
#include <set>
#include <numeric>
#include <iomanip>
#include <climits>
#include <functional>
#include <cassert>
#include <tuple>
using namespace std;
using ll = long long;

int N, K;
string S;
const int MAX = 510000;
const int MOD = 998244353;

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

// テーブルを作る前処理
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;
    }
}

// 二項係数計算
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();
    cin >> N >> K >> S;
    int cntn = 0, sumn = 0;
    if(S[0] == 'N') {
        cntn++;
        sumn++;
    } 
    for(int i = 1; i < N; ++i) {
        if(S[i] == 'N' && S[i-1] != 'C') cntn++;
        if(S[i] == 'N') sumn++;
    }
    ll ans = 0;

    for(int i = 1; i <= sumn-K; ++i) {
        ans += COM(cntn, i);
        ans %= MOD;
    }

    cout << ans << endl;

}