#include <bits/stdc++.h>
#define rep(i,j,k) for(int i=(j);i<=(k);i++)
#define per(i,j,k) for(int i=(j);i>=(k);i--)
#define uint unsigned int
#define ll long long
#define ull unsigned long long
#define db double
#define ldb long double
#define pii pair<int,int>
#define pll pair<ll,ll>
#define mkp make_pair
#define eb emplace_back
#define SZ(S) (int)S.size()
//#define mod 998244353
#define mod 1000000007
#define inf 0x3f3f3f3f
#define linf 0x3f3f3f3f3f3f3f3f
using namespace std;

template <class T>
void chkmax(T &x,T y){
    if(x < y) x = y;
}

template <class T>
void chkmin(T &x,T y){
    if(x > y) x = y;
}

inline int popcnt(int x){
    return __builtin_popcount(x);
}

inline int ctz(int x){
    return __builtin_ctz(x);
}

template <int P>
class mod_int
{
    using Z = mod_int;

private:
    static int mo(int x) { return x < 0 ? x + P : x; }

public:
    int x;
    int val() const { return x; }
    mod_int() : x(0) {}
    template <class T>
    mod_int(const T &x_) : x(x_ >= 0 && x_ < P ? static_cast<int>(x_) : mo(static_cast<int>(x_ % P))) {}
    bool operator==(const Z &rhs) const { return x == rhs.x; }
    bool operator!=(const Z &rhs) const { return x != rhs.x; }
    Z operator-() const { return Z(x ? P - x : 0); }
    Z pow(long long k) const
    {
        Z res = 1, t = *this;
        while (k)
        {
            if (k & 1)
                res *= t;
            if (k >>= 1)
                t *= t;
        }
        return res;
    }
    Z &operator++()
    {
        x < P - 1 ? ++x : x = 0;
        return *this;
    }
    Z &operator--()
    {
        x ? --x : x = P - 1;
        return *this;
    }
    Z operator++(int)
    {
        Z ret = x;
        x < P - 1 ? ++x : x = 0;
        return ret;
    }
    Z operator--(int)
    {
        Z ret = x;
        x ? --x : x = P - 1;
        return ret;
    }
    Z inv() const { return pow(P - 2); }
    Z &operator+=(const Z &rhs)
    {
        (x += rhs.x) >= P && (x -= P);
        return *this;
    }
    Z &operator-=(const Z &rhs)
    {
        (x -= rhs.x) < 0 && (x += P);
        return *this;
    }
    Z operator-()
    {
        return -x;
    }
    Z &operator*=(const Z &rhs)
    {
        x = 1ULL * x * rhs.x % P;
        return *this;
    }
    Z &operator/=(const Z &rhs) { return *this *= rhs.inv(); }
#define setO(T, o)                                  \
    friend T operator o(const Z &lhs, const Z &rhs) \
    {                                               \
        Z res = lhs;                                \
        return res o## = rhs;                       \
    }
    setO(Z, +) setO(Z, -) setO(Z, *) setO(Z, /)
#undef setO
    
    friend istream& operator>>(istream& is, mod_int& x)
    {
        long long tmp;
        is >> tmp;
        x = tmp;
        return is;
    }
    friend ostream& operator<<(ostream& os, const mod_int& x)
    {
        os << x.val();
        return os;
    }
};

using Z = mod_int<mod>;
Z power(Z p,ll k){
    Z ans = 1;
    while(k){
        if(k % 2 == 1) ans *= p;
        p *= p;
        k /= 2;
    }
    return ans;
}
int n,m;
int a[505];
Z fact[505],ifac[505];

Z f[505][505],dp[505][505],ed[505][505];//f[i][j] [1,i] 颜色用到了第 j 种.
int main(){
//    freopen("ex_suffix3.in","r",stdin);
//    freopen("test.out","w",stdout);
    scanf("%d%d",&n,&m);
    fact[0] = 1;
    rep(i,1,n) fact[i] = fact[i - 1] * i;
    ifac[n] = Z(1) / fact[n];
    per(i,n - 1,0) ifac[i] = ifac[i + 1] * (i + 1);

    rep(i,1,m) scanf("%d",&a[i]);
    f[0][0] = 1;
    rep(i,0,n){
        rep(j,0,m){
            dp[i][j] = f[i][j];
            dp[i + 1][j] -= f[i][j];
        }

//        printf("i=%d\n",i);
        rep(r,i,n){
            if(r > i){
                rep(j,0,m){
                    dp[r][j] += dp[r - 1][j]; 
                    ed[r][j] += ed[r - 1][j];
                }                
            }

            rep(j,0,m - 1){
                dp[r + 1][j + 1] -= dp[r][j];
                if(r + a[j + 1] <= n) dp[r + a[j + 1]][j + 1] += dp[r][j];
                ed[r + 1][j + 1] += dp[r][j];
                if(r + a[j + 1] <= n) ed[r + a[j + 1] + 1][j + 1] -= dp[r][j];
            }
            rep(j,0,m) f[r][j] += ed[r][j] * ifac[r - i];
/*            printf("r=%d\n",r);
            rep(j,0,m) printf("%d ",dp[r][j].val());
            printf("\n");
            rep(j,0,m) printf("%d ",ed[r][j].val());
            printf("\n");*/
        }
        rep(r,i,n){
            fill(dp[r],dp[r] + m + 1,0);
            fill(ed[r],ed[r] + m + 1,0);
        }
    }
    Z ans = 0;
    rep(j,0,m) ans += f[n][j];
    ans *= fact[n];
    printf("%d\n",ans.val());
	return 0;
}