// @author : jellyfish
// @file : 3711.cpp
// Fuck CCF,CCF wants my money.
#include <bits/stdc++.h>
using namespace std;
#define rd() ({int x(0);bool f(0);char ch(getchar());while(ch<'0'||ch>'9')f^=ch=='-',ch=getchar();while(ch>='0'&&ch<='9')x=(x<<1)+(x<<3)+(ch^48),ch=getchar();f?-x:x; })
#define mod 1000000007
typedef long long ll;
int n, m;
vector<int> a;
int fac[1000005];
void init()
{
    fac[0] = fac[1] = 1;
    for (int i = 2; i <= 1000000; ++i)
        fac[i] = (1ll * fac[i - 1] * i) % mod;
}
int env(ll base)
{
    ll ans = 1;
    int b = mod - 2;
    while (b)
    {
        if (b & 1)
            ans = ans * base % mod;
        base = base * base % mod;
        b >>= 1;
    }
    return ans;
}
int C(int a, int b)
{
    return 1ll * fac[a] * env(fac[b]) % mod * env(fac[a - b]) % mod;
}
int main()
{
    ll ans = 1;
    init();
    // cerr << "init finish" << endl;
    n = rd(), m = rd();
    a.resize(m + 1);
    for (int i = m; i >= 1; --i)
        a[i] = rd();
    // sort(a.begin() + 1, a.end(), [](int a, int b) -> int
    //  { return a > b; });
    // cerr << "sort finish" << endl;

    for (int i = 1; i <= m; ++i)
    {
        // cerr << "start turn " << i << endl;
        // cerr << "a: " << n - a[i] - (n / m) * (i - 1) << " b: " << n / m - 1 << endl;
        ans *= C(n - a[i] - (n / m) * (i - 1), n / m - 1);
        ans %= mod;
        // cerr << "turn " << i << " finish" << endl;
    }
    printf("%d\n", ans);
    return 0;
}