#include<bits/stdc++.h>
using namespace std;
#define int long long
int n,m;
int dp[(1<<22)+5];
const int mod=1e9+7;
int cond[22];
signed main(){
	cin>>n>>m;
	for(int i=0;i<m;i++){
		int u,v;
		cin>>u>>v;
		u--,v--;
		cond[v]|=(1<<u);
	}
	dp[0]=1;
	for(int i=1;i<(1<<n);i++){
		for(int j=0;j<n;j++){
			if(i&(1<<j)){
				if(((i^(1<<j))&cond[j])!=cond[j])continue;
				dp[i]+=dp[i^(1<<j)];
				if(dp[i]>=mod)dp[i]-=mod;
			}
		}
	}
	cout<<dp[(1<<n)-1]<<"\n";
	return 0;
}