#![allow(non_snake_case, unused_imports, unused_must_use)]
use std::io::{self, prelude::*};
use std::str;

fn main() {
    let (stdin, stdout) = (io::stdin(), io::stdout());
    let mut scan = Scanner::new(stdin.lock());
    let mut out = io::BufWriter::new(stdout.lock());

    macro_rules! input {
        ($T: ty) => {
            scan.token::<$T>()
        };
        ($T: ty, $N: expr) => {
            (0..$N).map(|_| scan.token::<$T>()).collect::<Vec<_>>()
        };
    }

    let N = input!(usize);
    let K = input!(usize);
    let S = input!(String).chars().collect::<Vec<_>>();

    let mut cnt = 0;
    let mut ncnt = 0;

    for i in 0..N {
        if S[i] == 'N' {
            if (i >= 1 && S[i - 1] != 'C') || i == 0 {
                cnt += 1;
            }

            ncnt += 1;
        }
    }

    let mut ans = 0;

    for k in 1..N {
        if ncnt < K + k {
            break;
        }

        ans += combination::combination(cnt, k);
    }

    writeln!(out, "{}", ans % 998_244_353);
}

pub mod combination {
    const M: usize = 3 * 100_010;
    const MOD: usize = 998_244_353;

    const fn comb() -> ([usize; M], [usize; M], [usize; M]) {
        let mut f = [0; M];
        let mut f_inv = [0; M];
        let mut inv = [0; M];

        f[0] = 1;
        f[1] = 1;
        f_inv[0] = 1;
        f_inv[1] = 1;
        inv[1] = 1;

        let mut i = 2;

        while i < M {
            f[i] = (f[i - 1] * i) % MOD;
            inv[i] = MOD - inv[MOD % i] * (MOD / i) % MOD;
            f_inv[i] = f_inv[i - 1] * inv[i] % MOD;

            i += 1;
        }

        return (f, f_inv, inv);
    }

    const _F: [usize; M] = comb().0;
    const _F_INV: [usize; M] = comb().1;
    const _INV: [usize; M] = comb().2;

    /// return nCk % MOD
    pub const fn combination(n: usize, k: usize) -> usize {
        if n < k {
            return 0;
        } else {
            return _F[n] * (_F_INV[k] * _F_INV[n - k] % MOD) % MOD;
        }
    }

    /// return n! % MOD
    pub const fn factorial(n: usize) -> usize {
        return _F[n];
    }
}

struct Scanner<R> {
    reader: R,
    buf_str: Vec<u8>,
    buf_iter: str::SplitWhitespace<'static>,
}
impl<R: BufRead> Scanner<R> {
    fn new(reader: R) -> Self {
        Self {
            reader,
            buf_str: vec![],
            buf_iter: "".split_whitespace(),
        }
    }
    fn token<T: str::FromStr>(&mut self) -> T {
        loop {
            if let Some(token) = self.buf_iter.next() {
                return token.parse().ok().expect("Failed parse");
            }
            self.buf_str.clear();
            self.reader
                .read_until(b'\n', &mut self.buf_str)
                .expect("Failed read");
            self.buf_iter = unsafe {
                let slice = str::from_utf8_unchecked(&self.buf_str);
                std::mem::transmute(slice.split_whitespace())
            }
        }
    }
}