#include<bits/stdc++.h>
#define Gc() getchar()
#define Me(x,y) memset(x,y,sizeof(x))
#define Mc(x,y) memcpy(x,y,sizeof(x))
#define d(x,y) ((m)*(x-1)+(y))
#define R(n) (rnd()%(n)+1)
#define Pc(x) putchar(x)
#define LB lower_bound
#define UB upper_bound
#define fi first
#define se second
#define eb emplace_back
#define all(x) x.begin(),x.end()
using namespace std;using ll=long long;using db=double;using lb=long db;using ui=unsigned;using ull=unsigned long long;using pii=pair<int,int>;
const int N=1e5+5,M=(1<<20)+5,K=1000+5,mod=998244353,Mod=mod-1;const db eps=1e-9;const ll INF=1e18+7;mt19937 rnd(263082);
#define Tp template<typename T>
#define Ts template<typename T,typename... Ar>
namespace Debug{
	Tp void _debug(char* f,T t){cerr<<f<<'='<<t<<endl;}
	Ts void _debug(char* f,T x,Ar... y){while(*f!=',') cerr<<*f++;cerr<<'='<<x<<",";_debug(f+1,y...);}
	#ifdef LOCAL
	#define gdb(...) _debug((char*)#__VA_ARGS__,__VA_ARGS__)
	#else 
	#define gdb(...) void()
	#endif
}using namespace Debug;
int n,m,vis[N];
ll dp[N],frc[N];
void Solve(){
	scanf("%d%d",&n,&m);
	while(m--){
		int x;scanf("%d",&x);
		vis[x]=1;
	}
	for(int i=1;i<2*n;i+=2) vis[i]&=vis[2*n-i];
	for(int i=frc[0]=1;i<=2*n;i++) frc[i]=frc[i-1]*i%mod;
	dp[0]=1;
	vis[0]=vis[2*n]=1;
	for(int i=1;i<=2*n;i++)if(vis[i]){
		for(int j=1;j<=i;j++) if(vis[j-1]) (dp[i]+=(mod-dp[j-1])*frc[i-j+1])%=mod;
		gdb(dp[i]);
	}
	printf("%lld\n",(mod-dp[2*n])%mod);
}
int main(){
	int t=1;
	// scanf("%d",&t);
	while(t--) Solve();
	cerr<<clock()*1.0/CLOCKS_PER_SEC<<'\n';
}