#include <bits/stdc++.h>
using namespace std;
using ll = long long;
const int MAX = 110000;
const int MOD = 1000000007;
long long fac[MAX], finv[MAX], inv[MAX];
void COMinit() {
  fac[0] = fac[1] = 1;
  finv[0] = finv[1] = 1;
  inv[1] = 1;
  for (int i = 2; i < MAX; i++) {
    fac[i] = fac[i - 1] * i % MOD;
    inv[i] = MOD - inv[MOD % i] * (MOD / i) % MOD;
    finv[i] = finv[i - 1] * inv[i] % MOD;
  }
}
long long COM(int n, int k) {
  if (n < k) return 0;
  if (n < 0 || k < 0) return 0;
  return fac[n] * (finv[k] * finv[n - k] % MOD) % MOD;
}
int main() {
  ll n, m;
  cin >> n >> m;
  vector<ll> a(m);
  for (int i = 0; i < m; i++) cin >> a[i];
  a.push_back(n + 1);
  COMinit();
  ll ans = 1;
  ll now = 0;
  for (int i = 0; i < a.size(); i++) {
    int dif = a[i] - now - 1;
    ll way = 0;
    for (int j = 0; 2 * j <= dif; j++) {
      way += COM(dif - j, j);
    }
    ans *= way;
    ans = (ans + MOD) % MOD;
    now = a[i] + 1;
  }
  cout << ans << endl;
}
