#include<bits/stdc++.h>
#define ll long long
using namespace std;
 ll n,m,s[2000000],cnt[2000000],unon[23];
ll temp;
void _init()
{
	scanf("%lld%lld",&n,&m);
	ll a,b;
	temp=(1<<n)-1;
	for(ll i=1;i<=m;i++)
	{
		scanf("%lld%lld",&a,&b);
		unon[a]|=(1<<(n-b));
	}
	for(ll i=1;i<=temp;i++)
	{
		
		cnt[i]=cnt[i>>1]+(i&1);
	}
	
}
ll lowbit(int x){return x&(-x);
}
int main()
{
	freopen("examone.in","r",stdin);
	freopen("examone.out","w",stdout);
	_init();
	s[0]=1;
	
	for(ll i=1;i<=temp;i++)
	  for(ll j=i;j;j-=lowbit(j))
	  {
	  	ll k=lowbit(j);
	  	if(k&unon[cnt[i]])continue;
	  	s[i]+=s[i-k];
	  }
	printf("%lld",s[temp]);
	return 0;
}