#include<bits/stdc++.h>
using namespace std;
using ll = long long;
//using LL = __int128
const int maxn = (1 << 23) + 5;
#define mod 1000000007ll
ll n, m, p[30], p1[30];
ll f[maxn];
vector<int> g[30];
bool vis[30][30];
void add(int u, int v){
	if(vis[v][u]){
		cout << 0;
		exit(0);
	}
	if(!vis[u][v])
		g[u].push_back(v), vis[u][v] = true;
}
bool check(){
	for(int i = 1 ; i <= n ; i++){
		for(auto v : g[i])
			if(p[i] >= p[v])
				return false;
	}
	return true;
}
int main(){
	//cout << sizeof(f);
	cin >> n >> m;
	for(int i = 1 ; i <= m ; i++){
		int u, v;
		cin >> u >> v;
		add(u, v);
		p1[u] |= (1 << v);
	}
	if(n <= 10){
		for(int i = 1 ; i <= n ; i++)
			p[i] = i;
		ll ans = 0;
		do{
			ans += check();
		}while(next_permutation(p + 1, p + 1 + n));
		cout << ans;
		exit(0);
	}
	f[0] = 1;
	for(int s = 0 ; s < (1 << (n + 1)) ; s += 2){
		//if(s == 2)
			//cout << (!(s >> (1 - 1)) & 1);
		for(int i = 1 ; i <= n ; i++)
			if(((p1[i] & s) == p1[i]) && (!((s >> i) & 1))){
				f[s | (1 << i)] = (f[s | (1 << i)] + f[s]) % mod;
				//cout << i << ":" << f[s] << " " << s << " " << f[s | (1 << (i - 1))] << " " << (s | (1 << (i - 1))) << "\n";
			}
	}
	cout << f[(1 << (n + 1)) - 2] << "\n";
	return 0;
}