#include<bits/stdc++.h>
#define For(i,a,b) for(int i=(a);i<=(b);++i)
#define Rof(i,a,b) for(int i=(a);i>=(b);--i)
using namespace std;
const int Maxn=(1<<12),Mod=998244353;

inline int Pow(int x,int y)
{
    int res=1;
    while(y)
    {
        if(y&1) res=1ll*res*x%Mod;
        x=1ll*x*x%Mod,y>>=1;
    }
    return res;
}

int n,m,all,a[15],b[15],fac[Maxn+5],inv[Maxn+5],lim;
int iv[Maxn+5],f[Maxn+5][Maxn+5],g[Maxn+5][Maxn+5],c[Maxn+5],s[Maxn+5];
inline int C(int x,int y) {return (x<y || y<0)?0:1ll*fac[x]*inv[x-y]%Mod*inv[y]%Mod;}

int main()
{
    // freopen("card.in","r",stdin);
    // freopen("card.out","w",stdout);

    cin>>n>>m; lim=(1<<m)-1;
    For(i,1,m) cin>>a[i];
    For(i,1,m) cin>>b[i],all+=b[i];
    fac[0]=inv[0]=1;
    For(i,1,Maxn) fac[i]=1ll*fac[i-1]*i%Mod;
    inv[Maxn]=Pow(fac[Maxn],Mod-2);
    Rof(i,Maxn-1,1) inv[i]=1ll*inv[i+1]*(i+1)%Mod;
    For(i,1,Maxn) iv[i]=Pow(i,Mod-2);
    int bgn=0; For(i,1,m) if(!b[i]) bgn|=(1<<i-1);
    f[0][bgn]=1; For(i,1,m) For(j,0,b[i]-1) f[0][bgn]=1ll*f[0][bgn]*(a[i]-j)%Mod;
    For(i,1,m) c[1<<i-1]=a[i]-b[i],s[1<<i-1]=b[i];
    For(i,1,lim) {int x=(i&(-i)),y=(x^i); if(y) c[i]=c[x]+c[y],s[i]=s[x]+s[y];}
    For(i,1,all) For(j,0,lim) if(f[i-1][j])
    {
        int res=f[i-1][j],val=g[i-1][j],cnt=c[j],sum=n-i+1;
        int p=iv[sum-cnt],c=1ll*sum*iv[sum-cnt]%Mod*p%Mod;
        // cerr<<sum<<' '<<1ll*p*sum%Mod<<endl;
        f[i][j]=(f[i][j]+1ll*res*p)%Mod;
        g[i][j]=(g[i][j]+1ll*val*p+1ll*res*c)%Mod;
        For(k,1,m) if(!(j&(1<<k-1)))
        {
            int now=C(i-1-s[j],b[k]-1); if(!now) continue;
            int p1=1ll*p*now%Mod,c1=1ll*c*now%Mod,j1=j|(1<<k-1);
            f[i][j1]=(f[i][j1]+1ll*res*p1)%Mod;
            g[i][j1]=(g[i][j1]+1ll*val*p1+1ll*res*c1)%Mod;
        }
    } cout<<g[all][lim]<<endl;
    return 0;
}