#include<bits/stdc++.h>
#define ll long long int
#define ull unsigned long long 
#define ff first
#define ss second
#define fast ios_base::sync_with_stdio(false); cin.tie(0); cout.tie(0);
#define pb push_back 
#define mp make_pair
#define inf 2000000009
#define mod 1000000007
#define ld long double
using namespace std;

int main()
{ 
    fast;
    ll n,k;
    cin>>n>>k;

    ll dp[k+2][n+2];
    memset(dp,0,sizeof(dp));
    dp[0][0]=1;

    ll f[10000],fi[10000],inv[10000];
    f[0]=f[1]=fi[0]=fi[1]=inv[0]=inv[1]=1;

    for(ll i=2;i<10000;i++)
    {
      f[i]=f[i-1]*i%mod;
      inv[i]=mod-inv[mod%i]*(mod/i)%mod;
      fi[i]=fi[i-1]*inv[i]%mod;
    }

    ll ans=f[n];
    ll ak;

    for(ll i=1;i<=k;i++)
    {
      cin>>ak;
     for(ll prev=0;prev<=n ;prev++)
     {
      for(ll cur=0;cur+prev<=n and cur<=ak;cur++)
        dp[i][cur+prev]=(dp[i][cur+prev]+ dp[i-1][prev]*f[n-cur]%mod*fi[cur]%mod*fi[ak-cur]%mod*fi[n-ak]%mod)%mod;
     }
    }
    cout<<f[n]*dp[k][n]%mod<<endl;
}