#include <bits/stdc++.h>
using namespace std;
const int INF = INT_MAX;
const int MAX = 510000;
const long long 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() {
  long long n, k;
  cin >> n >> k;
  vector<long long> a(k + 2, -1);
  COMinit();
  for (long long i = (0); i < (k); ++i) {
    cin >> a[i + 1];
  }
  a[k + 1] = n + 1;
  long long ans = 1;
  for (long long i = (0); i < (k + 1); ++i) {
    long long tmp = a[i + 1] - a[i] - 2;
    if (tmp <= 0) {
      if (a[i] == -1 || a[i + 1] == n + 1) {
        continue;
      } else {
        cout << 0 << endl;
        return 0;
      }
    }
    long long x = 0;
    for (long long j = (0); j < ((tmp / 2) + 1); ++j) {
      x += COM(tmp - j, j);
      x %= MOD;
    }
    ans *= x;
    ans %= MOD;
  }
  cout << ans << endl;
}
