#include <bits/stdc++.h>
using namespace std;
#include <atcoder/convolution>
using mint = atcoder::modint998244353;
#define rep(i, a, b) for (int i = a; i < b; i++)

mint solve(int N, vector<int> A){
    vector<mint> fact(N + 1, 1);
    rep(i, 1, N + 1) fact[i] = fact[i - 1] * i;
    if (N <= 2){
        if ((int)A.size() & 1) return 0;
        return fact[N];
    }
    vector<int> p(N);
    int c = 1;
    for (auto x : A){
        p[x - 1] = 1;
        if (x == 1 || x == N) c *= -1;
    }
    vector<mint> dp(N);
    p[0] = 1, p[N - 1] = 1;
    dp[0] = 1;
    auto f = [&](auto self, int l, int r) -> void {
        if (l + 1 == r){
            if (p[l]) dp[l] *= -2;
            else dp[l] = 0;
            return;
        }
        int m = (l + r) / 2;
        self(self, l, m);
        vector<mint> Y(r - l);
        rep(i, 0, r - l) Y[i] = fact[i + 1];
        vector<mint> X(m - l);
        rep(i, l, m) X[i - l] = dp[i];
        auto Z = atcoder::convolution(X, Y);
        rep(i, m, r) dp[i] += Z[i - l];
        self(self, m, r);
    };
    f(f, 0, N);
    mint ans = (fact[N] + dp[N - 1] / 4) / 2;
    if (c == -1) ans = fact[N] - ans;
    return ans;
}


int main(){
	std::ios::sync_with_stdio(false);
    std::cin.tie(nullptr);

	int N, M;
	cin >> N >> M;
    
    vector<int> A(M);
    rep(i, 0, M) cin >> A[i];

    cout << solve(N, A).val() << "\n";
}