#include <bits/stdc++.h>
using namespace std;

#define FOR(i, a, b) for(int i = (a); i < (b); i++)
#define RFOR(i, a, b) for(int i = (a) - 1; i >= (b); i--)
#define SZ(a) int(a.size())
#define ALL(a) a.begin(), a.end()
#define PB push_back
#define MP make_pair
#define F first
#define S second

typedef long long LL;
typedef vector<int> VI;
typedef vector<LL> VL;
typedef pair<int, int> PII;
typedef pair<LL, LL> PLL;
typedef double db;

const int mod = 1e9 + 7;
void updAdd(int& a, int b)
{
	a += b;
	if(a >= mod)
		a -= mod;
}

int main()
{
	ios::sync_with_stdio(0); 
	cin.tie(0);
	
	int n, m;
	cin >> n >> m;
	
	n += 2;
	VI a(n);
	FOR(i, 0, m)
	{
		int p;
		cin >> p;
		a[p]++;
	}
	VI pref(n + 1);
	FOR(i, 0, n)
		pref[i + 1] = pref[i] + a[i];
	
	VI dp(n);
	dp[0] = 1;
	
	VI vals(m + n + 1);
	
	FOR(j, 0, n)
	{
		if(j != 0 && a[j] == 0)
			dp[j] = vals[pref[j] - j + n];
		updAdd(vals[pref[j + 1] - (j + 1) + n], dp[j]);
	}
	cout << dp[n - 1] << "\n";
	
	




	return 0;
}