#include<bits/stdc++.h>
using namespace std;
typedef unsigned long long int ull;
typedef long long int ll;
typedef pair<ll,ll> pll;
typedef long double D;
//typedef complex<D> P;
#define F first
#define S second
const ll MOD=1000000007;
//const ll MOD=998244353;

template<typename T,typename U>istream & operator >> (istream &i,pair<T,U> &A){i>>A.F>>A.S; return i;}
template<typename T>istream & operator >> (istream &i,vector<T> &A){for(auto &I:A){i>>I;} return i;}
template<typename T,typename U>ostream & operator << (ostream &o,const pair<T,U> &A){o<<A.F<<" "<<A.S; return o;}
template<typename T>ostream & operator << (ostream &o,const vector<T> &A){int i=A.size(); for(auto &I:A){o<<I<<(--i?" ":"");} return o;}



template<long long int mod=1000000007>
struct Mod_Int{
    typedef long long int ll;
    typedef pair<ll,ll> pll;
    typedef Mod_Int<mod> M;
    ll a;
    
    ll mod_pow(ll a,ll x){
        a%=mod;
        ll ans=1;
        for(int i=0;i<63;i++){
            if(x>>i&1){ans*=a; ans%=mod;}
            a*=a;
            a%=mod;
        }
        return ans;
    }
    
    pll Ex_gcd(ll a,ll b){
        if(b==0){return {1,0};}
        pll ret=Ex_gcd(b,a%b);
        ret.F-=a/b*ret.S;
        return {ret.S,ret.F};
    }
    
    ll prime_R(ll a){
        return mod_pow(a,mod-2);
    }
    
    ll R(ll a){
        ll ret=Ex_gcd(a,mod).F;
        ret%=mod;
        if(ret<0){ret+=mod;}
        return ret;
    }
    
    Mod_Int(ll A=1):a(A){
        a%=mod;
        if(a<0){a+=mod;}
    }
    
    Mod_Int(const M &b):a(b.a){}
    
    M & operator += (const M &b){
        a+=b.a;
        if(a>=mod){a-=mod;}
        return *this;
    }
    
    M operator + (const M &b) const {
        M c=*this;
        return c+=b;
    }
    
    M & operator -= (const M &b){
        a-=b.a;
        if(a<0){a+=mod;}
        return *this;
    }
    
    M operator - (const M &b) const {
        M c=*this;
        return c-=b;
    }
    
    M & operator *= (const M &b){
        (a*=b.a)%=mod;
        return *this;
    }
    
    M operator * (const M &b) const {
        M c=*this;
        return c*=b;
    }
    
    M & operator /= (const M &b){
        (a*=R(b.a))%=mod;
        return *this;
    }
    
    M operator / (const M &b) const {
        M c=*this;
        return c/=b;
    }
    
    M & mod_pow_equal(ll x){
        ll ans=1;
        while(x>0){
            if(x&1){ans*=a; ans%=mod;}
            a*=a;
            a%=mod;
            x>>=1;
        }
        a=ans;
        return *this;
    }
    
    M mod_pow(ll x){
        M c(a);
        return c.mod_pow_equal(x);
    }
    
    bool operator == (const M &b) const {return a==b.a;}
    
    bool operator != (const M &b) const {return a!=b.a;}
    
    bool operator <= (const M &b) const {return a<=b.a;}
    
    bool operator < (const M &b) const {return a<b.a;}
    
    bool operator > (const M &b) const {return a>b.a;}
    
    bool operator >= (const M &b) const {return a>=b.a;}
    
    M & operator = (const M &b){
        a=b.a;
        return *this;
    }
    
    M & operator = (const ll &b){
        (a=b)%=mod;
        if(a<0){a+=mod;}
        return *this;
    }
};

template<long long MOD>istream & operator >> (istream &i,Mod_Int<MOD> &A){ll a; cin>>a; A=Mod_Int<MOD>(a); return i;}
template<long long MOD>ostream & operator << (ostream &i,const Mod_Int<MOD> &A){i<<A.a; return i;}


using Int=Mod_Int<MOD>;

class comb{
private:
    ll mod;
    ll mx;
    vector<ll> F;
    vector<ll> FR;
    
public:
    comb(ll mod=1000000007,ll mx=100000):mod(mod),mx(mx),F(mx+1,1),FR(mx+1,1){
        mk_F();
    }
    
    ll mod_pow(ll a,ll x){
        a%=mod;
        ll ans=1;
        while(x>0){
            if(x&1){ans*=a; ans%=mod;}
            a*=a;
            a%=mod;
            x>>=1;
        }
        return ans;
    }
    
    pll Ex_gcd(ll a,ll b){
        if(b==0){return {1,0};}
        pll ret=Ex_gcd(b,a%b);
        ret.F-=a/b*ret.S;
        return {ret.S,ret.F};
    }
    
    ll prime_R(ll a){
        return mod_pow(a,mod-2);
    }
    
    ll R(ll a){
        ll ret=Ex_gcd(a,mod).F;
        ret%=mod;
        if(ret<0){ret+=mod;}
        return ret;
    }
    
    void mk_F(){
        for(ll i=1;i<=mx;i++){F[i]=F[i-1]*i%mod; FR[i]=R(F[i]);}
    }
    
    ll c(ll n,ll k){
        if(n<k || k<0 || n<0){return 0;}
        if(n==k || k==0){return 1;}
        return F[n]*FR[n-k]%mod*FR[k]%mod;
    }
    
    //mod must be prime
    ll Lucas_C(ll n,ll m){
        ll ret=1;
        while(n>0 || m>0){
            ret*=c(n%mod,m%mod);
            ret%=mod;
            n/=mod; m/=mod;
        }
        return ret;
    }
    
    ll Stirling(ll n,ll k){
        ll ret=0;
        for(ll i=1;i<=k;i++){
            if((k-i)%2){ret-=c(k,i)*mod_pow(i,n)%mod;}
            else{ret+=c(k,i)*mod_pow(i,n)%mod;}
            ret%=mod;
        }
        ret*=R(F[k]);
        ret%=mod;
        if(ret<0){ret+=mod;}
        return ret;
    }
    
    ll Bell(ll n,ll k){
        ll ret=0;
        for(ll i=1;i<=k;i++){ret+=Stirling(n,i); ret%=mod;}
        return ret;
    }
};

comb C(MOD,100000);


int main(){
  cin.tie(0);
  ios::sync_with_stdio(false);
  ll N,K;
  cin>>N>>K;
  vector<ll> A(K);
  cin>>A;
  vector<vector<Int>> dp(K+1,vector<Int>(N+1,0));
  dp[0][0]=1;
  for(int i=0;i<K;i++){
    for(int j=0;j<=N;j++){
      for(int k=0;k<=A[i] && j+k<=N;k++){
        dp[i+1][j+k]+=dp[i][j]*Int(C.c(N-j,k))*C.c(N-k,A[i]-k);
      }
    }
  }
  cout<<dp[K][N]<<endl;


  return 0;
}


Measured memory_bytes: 2048