#include<cstdio>
    #include<iostream>
    using namespace std;
    long long n,m,f[1048576]={0},p[21]={0},a[21],t,c;
    int main()
    {
    	freopen("arrange.in","r",stdin);
    	freopen("arrange.out","w",stdout);
    	scanf("%d%d",&n,&m);
    	p[0]=1;
    	for(int i=1;i<=n;i++)
    		p[i]=p[i-1]*2;
    	//printf("%d",p[n]);
    	for(int i=1;i<=m;i++)
    	{
    		int x,b;
    		scanf("%d%d",&x,&b);
    		a[x]+=p[b-1];
    	}
    	f[0]=1;
    	for(int i=1;i<p[n];i++)
    	{
    		for(c=0,t=i;t;c++,t-=(t&-t));
    		for(t=i&~a[c];t;t-=(t&-t))
    			f[i]+=f[i^(t&-t)];
    		//cout<<f[i]<<endl;
    	}
    	printf("%lld",f[p[n]-1]);
    	return 0;
    }