#include <bits/stdc++.h>
using namespace std;
using ll = int64_t;
using pint = pair<int, int>;
const int mod = 1000000007;
struct mint {
  ll x;
  mint(ll x = 0) : x((x % mod + mod) % mod) {}
  mint operator-() const { return mint(-x); }
  mint &operator+=(const mint a) {
    if ((x += a.x) >= mod) x -= mod;
    return *this;
  }
  mint &operator-=(const mint a) {
    if ((x += mod - a.x) >= mod) x -= mod;
    return *this;
  }
  mint &operator*=(const mint a) {
    (x *= a.x) %= mod;
    return *this;
  }
  mint operator+(const mint a) const { return mint(*this) += a; }
  mint operator-(const mint a) const { return mint(*this) -= a; }
  mint operator*(const mint a) const { return mint(*this) *= a; }
  mint pow(ll t) const {
    if (!t) return 1;
    mint a = pow(t >> 1);
    a *= a;
    if (t & 1) a *= *this;
    return a;
  }
  mint inv() const { return pow(mod - 2); }
  mint &operator/=(const mint a) { return *this *= a.inv(); }
  mint operator/(const mint a) const { return mint(*this) /= a; }
};
istream &operator>>(istream &is, const mint &a) { return is >> a.x; }
ostream &operator<<(ostream &os, const mint &a) { return os << a.x; }
struct combination {
  vector<mint> fact, ifact;
  combination(int n) : fact(n + 1), ifact(n + 1) {
    assert(n < mod);
    fact[0] = 1;
    for (int i = 1; i <= n; ++i) fact[i] = fact[i - 1] * i;
    ifact[n] = fact[n].inv();
    for (int i = n; i >= 1; --i) ifact[i - 1] = ifact[i] * i;
  }
  mint operator()(int n, int k) {
    if (k < 0 || k > n) return 0;
    return fact[n] * ifact[k] * ifact[n - k];
  }
};
int main() {
  int n, m;
  cin >> n >> m;
  vector<int> a(m);
  for (int i = 0; i < (m); ++i) cin >> a[i];
  mint ans = 1;
  int prev = 0;
  for (int i = 0; i < (m); ++i) {
    int x = a[i] - prev - 1;
    prev = a[i] + 1;
    int p = x / 2;
    mint tmp = (x == -1) ? 0 : 1;
    if (tmp.x == 0) {
      cout << 0 << endl;
      return 0;
    }
    while (p > 0) {
      combination c(x - p);
      tmp += c(x - p, p);
      --p;
    }
    ans *= tmp;
  }
  int x = n - prev;
  int p = x / 2;
  mint tmp = (x == -1) ? 0 : 1;
  while (p > 0) {
    combination c(x - p);
    tmp += c(x - p, p);
    --p;
  }
  ans *= tmp;
  cout << ans << endl;
}
