#include <bits/stdc++.h>
using namespace std;
using ll = long long;
const int MOD = 1000000007;
void scan(int& a) { scanf("%d", &a); }
void scan(long long& a) { scanf("%lld", &a); }
template <class T>
void scan(T& a) {
  cin >> a;
}
template <class T>
void scan(vector<T>& vec) {
  for (auto&& it : vec) scan(it);
}
void in() {}
template <class Head, class... Tail>
void in(Head& head, Tail&... tail) {
  scan(head);
  in(tail...);
}
void print(const int& a) { printf("%d", a); }
void print(const long long& a) { printf("%lld", a); }
void print(const double& a) { printf("%.15lf", a); }
template <class T>
void print(const T& a) {
  cout << a;
}
template <class T>
void print(const vector<T>& vec) {
  if (vec.empty()) return;
  print(vec[0]);
  for (auto it = vec.begin(); ++it != vec.end();) {
    putchar(' ');
    print(*it);
  }
}
void out() { putchar('\n'); }
template <class T>
void out(const T& t) {
  print(t);
  putchar('\n');
}
template <class Head, class... Tail>
void out(const Head& head, const Tail&... tail) {
  print(head);
  putchar(' ');
  out(tail...);
}
template <class T>
void dprint(const T& a) {
  cerr << a;
}
template <class T>
void dprint(const vector<T>& vec) {
  if (vec.empty()) return;
  cerr << vec[0];
  for (auto it = vec.begin(); ++it != vec.end();) {
    cerr << " " << *it;
  }
}
void debug() { cerr << endl; }
template <class T>
void debug(const T& t) {
  dprint(t);
  cerr << endl;
}
template <class Head, class... Tail>
void debug(const Head& head, const Tail&... tail) {
  dprint(head);
  cerr << " ";
  debug(tail...);
}
vector<vector<long long int>> combination_calc(10000,
                                               vector<long long int>(10000, 0));
long long int combination2(long long int n, long long int k) {
  if (combination_calc[n][k] != 0) {
    return combination_calc[n][k];
  } else if (k == 0) {
    combination_calc[n][0] = 1;
    return 1;
  } else if (k == n) {
    combination_calc[n][n] = 1;
    return 1;
  } else {
    combination_calc[n][k] =
        (combination2(n - 1, k - 1) + combination2(n - 1, k)) % MOD;
    return combination_calc[n][k];
  }
}
int main() {
  ll n, m;
  in(n, m);
  vector<int> vec(m);
  in(vec);
  vec.push_back(n + 1);
  ll target = 0, ans = 1, d = 0;
  for (int i = 0; i < (int)(m + 1); i++) {
    if (i == 0)
      target = vec[i] - 1;
    else
      target = vec[i] - vec[i - 1] - 2;
    if (target == -1) {
      ans = 0;
      break;
    }
    d = 0;
    if (target == 0)
      d = 1;
    else if (target == 1)
      d = 1;
    else if (target == 2)
      d = 2;
    else if (target >= 3) {
      for (ll two = 0; 2 * two <= target; two++) {
        ll one = target - 2 * two;
        d += combination2(one + two, two);
        if (d > MOD) d %= MOD;
      }
    }
    ans *= d;
    if (ans > MOD) ans %= (ll)MOD;
  }
  out(ans);
}
