import java.io.*;
import java.util.*;
import java.util.function.*;
import java.util.stream.*;

public class Main {
    static final int MOD = 998244353;
    public static void main(String[] args) throws Exception {
        Scanner sc = new Scanner();
        int n = sc.nextInt();
        int k = sc.nextInt();
        char[] input = sc.next().toCharArray();
        int count = 0;
        int target = 0;
        char prev = 'N';
        for (char c : input) {
            if (c == 'N') {
                count++;
                if (prev != 'C') {
                    target++;
                }
            }
            prev = c;
        }
        long ans = 0;
        Combination comb = new Combination(target + 3);
        for (int i = 1; i <= count - k && i <= target; i++) {
            ans += comb.getComb(target, i);
            ans %= MOD;
        }
        System.out.println(ans);
    }
}
class Combination {
    static final int MOD = 998244353;
    long[] fac;
    long[] finv;
    long[] inv;
    
    public Combination (int size) {
        fac = new long [size];
        finv = new long [size];
        inv = new long [size];
        fac[0] = 1;
        fac[1] = 1;
        finv[0] = 1;
        finv[1] = 1;
        inv[1] = 1;
        for (int i = 2; i < size; 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;
        }
    }
    
    
    public long getComb(int n, int k) {
        if (n < k || n < 0 || k < 0) {
            return 0;
        }
        return fac[n] * (finv[k] * finv[n - k] % MOD) % MOD;
    }
    
}

class Scanner {
    BufferedReader br;
    StringTokenizer st = new StringTokenizer("");
    StringBuilder sb = new StringBuilder();
    
    public Scanner() {
        try {
            br = new BufferedReader(new InputStreamReader(System.in));
        } catch (Exception e) {
            
        }
    }
    
    public int nextInt() {
        return Integer.parseInt(next());
    }
    
    public long nextLong() {
        return Long.parseLong(next());
    }
    
    public double nextDouble() {
        return Double.parseDouble(next());
    }
    
    public String next() {
        try {
            while (!st.hasMoreTokens()) {
                st = new StringTokenizer(br.readLine());
            }
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            return st.nextToken();
        }
    }
    
}