#include<bits/stdc++.h>
using namespace std;

#define int long long

const int N=1000+5,M=12+5,mod=998244353;

int POW(int a,int b){
	int res=1;a%=mod;
	while(b){
		if(b&1)res=res*a%mod;
		a=a*a%mod,b>>=1;
	}
	return res;
}
int divi(int a,int b){return a*POW(b,mod-2)%mod;}

int frac[N],ifrac[N],inv[N];
int binum(int a,int b){return frac[a]*ifrac[a-b]%mod*ifrac[b]%mod;}

int n,m,sum,a[M],b[M];
int A,sa[(1<<12)+5],sb[(1<<12)+5];

int dp[2][(1<<12)+5],g[2][(1<<12)+5];

signed main(){
	
	cin>>n>>m;
	for(int i=1;i<=m;i++)cin>>a[i];
	for(int i=1;i<=m;i++)cin>>b[i],sum+=b[i];

	frac[0]=1;
	for(int i=1;i<=n;i++)frac[i]=frac[i-1]*i%mod;
	ifrac[n]=POW(frac[n],mod-2);
	for(int i=n-1;i>=0;i--)ifrac[i]=ifrac[i+1]*(i+1)%mod;
	for(int i=1;i<=n;i++)inv[i]=frac[i-1]*ifrac[i]%mod;

	A=1;
	for(int i=1;i<=m;i++)for(int j=0;j<b[i];j++)A=A*(a[i]-j)%mod;

	for(int i=0;i<(1<<m);i++)
		for(int j=1;j<=m;j++)
			if((i>>(j-1))&1)sa[i]+=a[j],sb[i]+=b[j];

	int f=0,st=0;
	for(int i=1;i<=m;i++)if(!b[i])st|=1<<(i-1);
	dp[0][st]=0,g[0][st]=1;
	for(int i=0;i<sum;i++,f^=1){
		memset(dp[f^1],0,sizeof(dp[f^1]));
		memset(g[f^1],0,sizeof(g[f^1]));
		for(int j=0;j<(1<<m);j++){
			if(i<sb[j])continue;
			int t=inv[(n-i)-sa[j]+sb[j]];
			int ndp=(n-i)*t%mod*t%mod*g[f][j]%mod,ng=t;
			(dp[f^1][j]+=ndp%mod+dp[f][j]*ng%mod)%=mod;
			(g[f^1][j]+=ng*g[f][j]%mod)%=mod;
			for(int k=1;k<=m;k++){
				if(i+1<sb[j]+b[k])continue;
				if(!b[k])continue;
				if((j>>(k-1))&1)continue;
				int t1=ndp*binum(i-sb[j],b[k]-1)%mod,t2=ng*binum(i-sb[j],b[k]-1)%mod;
				(dp[f^1][j|(1<<(k-1))]+=t1+t2*dp[f][j]%mod)%=mod;
				(g[f^1][j|(1<<(k-1))]+=t2*g[f][j]%mod)%=mod;
			}
		}
	}
	int ans=dp[f][(1<<m)-1]*A%mod;
	printf("%lld\n",ans);
	return 0;
}