#line 1 "h.cpp"
#include <bits/stdc++.h>
using namespace std;
#define rep(i,a,b) for (int i=(int)(a);i<(int)(b);i++)

#line 2 "/Users/Shared/po167_library/math/Binomial.hpp"

#line 5 "/Users/Shared/po167_library/math/Binomial.hpp"

namespace po167{
template<class T>
struct Binomial{
    std::vector<T> fact_vec, fact_inv_vec;
    void extend(int m = -1){
        int n = fact_vec.size();
        if (m == -1) m = n * 2;
        if (n >= m) return;
        fact_vec.resize(m);
        fact_inv_vec.resize(m);
        for (int i = n; i < m; i++){
            fact_vec[i] = fact_vec[i - 1] * T(i);
        }
        fact_inv_vec[m - 1] = T(1) / fact_vec[m - 1];
        for (int i = m - 1; i > n; i--){
            fact_inv_vec[i - 1] = fact_inv_vec[i] * T(i);
        }
    }
    Binomial(int MAX = 0){
        fact_vec.resize(1, T(1));
        fact_inv_vec.resize(1, T(1));
        extend(MAX + 1);
    }

    T fact(int i){
        if (i < 0) return 0;
        while (int(fact_vec.size()) <= i) extend();
        return fact_vec[i];
    }
    T invfact(int i){
        if (i < 0) return 0;
        while (int(fact_inv_vec.size()) <= i) extend();
        return fact_inv_vec[i];
    }
    T C(int a, int b){
        if (a < b || b < 0) return 0;
        return fact(a) * invfact(b) * invfact(a - b);
    }
    T invC(int a, int b){
        if (a < b || b < 0) return 0;
        return fact(b) * fact(a - b) *invfact(a);
    }
    T P(int a, int b){
        if (a < b || b < 0) return 0;
        return fact(a) * invfact(a - b);
    }
    T inv(int a){
        if (a < 0) return inv(-a) * T(-1);
        if (a == 0) return 1;
        return fact(a - 1) * invfact(a);
    }
    T Catalan(int n){
        if (n < 0) return 0;
        return fact(2 * n) * invfact(n + 1) * invfact(n);
    }
    T narayana(int n, int k){
        if (n <= 0 || n < k || k < 1) return 0;
        return C(n, k) *  C(n, k - 1) * inv(n);
    }
    T Catalan_pow(int n,int d){
        if (n < 0 || d < 0) return 0;
        if (d == 0){
            if (n == 0) return 1;
            return 0;
        }
        return T(d) * inv(d + n) * C(2 * n + d - 1, n);
    }
    // retrun [x^a] 1/(1-x)^b
    T ruiseki(int a,int b){
        if (a < 0 || b < 0) return 0;
        if (a == 0){
            return 1;
        }
        return C(a + b - 1, b - 1);
    }
    // (a, b) -> (c, d)
    // always x + e >= y
    T mirror(int a, int b, int c, int d, int e = 0){
        if (a + e < b || c + e < d) return 0;
        if (a > c || b > d) return 0;
        a += e;
        c += e;
        return C(c + d - a - b, c - a) - C(c + d - a - b, c - b + 1); 
    }
    // return sum_{i = 0, ... , a} sum_{j = 0, ... , b} C(i + j, i)
    // return C(a + b + 2, a + 1) - 1;
    T gird_sum(int a, int b){
        if (a < 0 || b < 0) return 0;
        return C(a + b + 2, a + 1) - 1;
    }
    // return sum_{i = a, ..., b - 1} sum_{j = c, ... , d - 1} C(i + j, i)
    // AGC 018 E
    T gird_sum_2(int a, int b, int c, int d){
        if (a >= b || c >= d) return 0;
        a--, b--, c--, d--;
        return gird_sum(a, c) - gird_sum(a, d) - gird_sum(b, c) + gird_sum(b, d);
    }

    // the number of diagonal dissections of a convex n-gon into k+1 regions.
    // OEIS A033282
    // AGC065D
    T diagonal(int n, int k){
        if (n <= 2 || n - 3 < k || k < 0) return 0;
        return C(n - 3, k) * C(n + k - 1, k) * inv(k + 1);
    }
};
}
#line 2 "/Users/Shared/po167_library/fps/FPS_online_convolution.hpp"
#include <atcoder/convolution>

namespace po167{
template<class T>
struct FPS_online_convolution{
    std::vector<T> f, g, h, iz;
    std::vector<std::vector<T>> f_inv, g_inv;
    int p;
    FPS_online_convolution() : f(0), g(0), h(0), iz(0), p(0){}
    T query(T fi, T gi){
        if (p == 0){
            f = {fi};
            g = {gi};
            h = {fi * gi};
            return h[p++];
        }
        int z = 0;
        while ((p & (1 << z)) == 0) z++;
        if (p == (1 << z)){
            f.resize(p * 2, 0);
            g.resize(p * 2, 0);
            h.resize(p * 2, 0);
        }
        f[p] = fi;
        g[p] = gi;
        int l = p - (1 << z);
        int m = p;
        int r = p + (1 << z);
        // [l, m) -> [m, r)
        std::vector<T> tmp3(r - l);
        if (l == 0){
            f_inv.push_back({});
            g_inv.push_back({});
            iz.push_back((T)(1) / (T)(r - l));
        }
        for (int rp = 0; rp < 2; rp++){
            std::swap(f, g);
            std::swap(f_inv, g_inv);
            if (l == 0 && rp == 1) break;
            std::vector<T> tmp1(r - l), tmp2(r - l);
            for (int i = l; i < m; i++){
                tmp1[i - l] = f[i];
            }
            atcoder::internal::butterfly(tmp1);
            if (l == 0) {
                for (int i = 0; i < r - l; i++) {
                    if (i == 0) continue;
                    if (m <= i) break;
                    tmp2[i] = g[i];
                }
                atcoder::internal::butterfly(tmp2);
            }
            else{
                if (g_inv[z].empty()){
                    g_inv[z].resize((1 << (z + 1)));
                    for (int i = 0; i < (1 << (z + 1)); i++){
                        if (i) g_inv[z][i] = g[i];
                        else g_inv[z][i] = 0;
                    }
                    atcoder::internal::butterfly(g_inv[z]);
                }
                tmp2 = g_inv[z];
            }
            for (int i = 0; i < r - l; i++) tmp3[i] += tmp1[i] * tmp2[i];
        }
        atcoder::internal::butterfly_inv(tmp3);
        for (int i = m; i < r; i++) h[i] += tmp3[i - l] * iz[z];
        h[p] += f[0] * g[p];
        h[p] += f[p] * g[0];
        return h[p++];
    }
};
}
#line 7 "h.cpp"
using mint = atcoder::modint998244353;

void solve();
// DEAR MYSTERIES / TOMOO
int main() {
    ios::sync_with_stdio(false);
    cin.tie(nullptr);

    int t = 1;
    // cin >> t;
    rep(i, 0, t) solve();
}

void solve(){
    int N, M;
    cin >> N >> M;
    vector<int> p(N);
    rep(i, 0, M){
        int a;
        cin >> a;
        p[a - 1] = 1;
    }
    po167::Binomial<mint> table;
    int c = 1;
    mint dp = -2;
    if (p[0] == 0){
        p[0] = 1;
        c *= -1;
    }
    if (p[N - 1] == 0){
        p[N - 1] = 1;
        c *= -1;
    }
    po167::FPS_online_convolution<mint> oc;
    rep(i, 1, N){
        dp = oc.query(table.fact(i + 1), dp);
        if (p[i] == 0) dp = 0;
        else dp *= -2;
    }
    mint ans = (dp / 4 + table.fact(N)) / 2;
    if (c == -1) ans = table.fact(N) - ans;
    cout << ans.val() << "\n";
}