package main

import . "fmt"
import . "math/big"

func main() {
	var n,k int
	var s string
	Scan(&n,&k,&s)
	var ns, cns int
	for i, c := range s {
		if c == 'N' {
			ns++
			if i > 0 && s[i-1] == 'C' {
				cns++
			}
		}
	}
	ns -= cns
	k = max(0, k-cns)
	if ns <= k {
		Println(0)
		return
	}
	const Mod = 998244353
	cc := make([]int, ns+1)
	cc[0] = 1
	for i := range cc[1:] {
		cc[i+1] = (cc[i]*(i+1))%Mod
	}
	dd := make([]int, ns+1)
	dd[ns] = int(new(Int).ModInverse(NewInt(int64(cc[ns])),NewInt(Mod)).Int64())
	for i := range dd[1:] {
		j := ns-i
		dd[j-1] = (dd[j]*j)%Mod
	}
	ans := 0
	for i := 1; i <= ns-k; i++ {
		ans += cc[ns]*dd[i]%Mod*dd[ns-i]%Mod
		ans %= Mod
	}
	Println(ans)
}