#include<cstdio>
#include<cstring>
#include<cstdlib>
#include<ctime>
#include<cmath>
#include<iostream>
#include<algorithm>
#define FILE "arrange"
typedef long long ll;
namespace IO{
	char buf[1<<15],*fs,*ft;
	inline char getc(){return (fs==ft&&(ft=(fs=buf)+fread(buf,1,1<<15,stdin),fs==ft))?0:*fs++;}
	inline int read(){
		int x=0,rev=0,ch=getc();
		while(ch<'0'||ch>'9'){if(ch=='-')rev=1;ch=getc();}
		while(ch>='0'&&ch<='9'){x=(x<<1)+(x<<3)+ch-'0';ch=getc();}
		return rev?-x:x;
	}
}using namespace IO;
const int MAXN(20),D(10);
//namespace Queue{
	struct queue{
		int num[1<<MAXN],fro,rear;
		inline void clear(){fro=0,rear=-1;}
		inline void push(int x){num[++rear]=x;}
		inline int pop(){return num[fro++];}
		inline bool empty(){return fro>rear;}
	}q[2];
//}using namespace Queue;
int n;
bool able[MAXN+D][MAXN+D];
ll f[2][1<<MAXN];
void init(){
	n=read();
	memset(able,1,sizeof able);
	int m=read();
	while(m--){
		int x=read(),y=read()-1;
		able[x][y]=false;
	}
}
void work(){
	f[0][0]=1;
	q[0].clear();q[0].push(0);
	for(int i=1;i<=n;i++){
		int now=i&1,prev=now^1;
		q[now].clear();
		memset(f[now],0,sizeof f[now]);
		while(!q[prev].empty()){
			int S=q[prev].pop();
			ll cnt=f[prev][S];
			for(int j=0;j<n;j++)
				if(((S>>j)&1)==0&&able[i][j]){
					int nS=S|(1<<j);
					if(!f[now][nS])q[now].push(nS);
					f[now][nS]+=cnt;
				}
		}
	}
	printf("%lld\n",f[n&1][(1<<n)-1]);
}
int main(){
	freopen(FILE".in","r",stdin);
	freopen(FILE".out","w",stdout);
	init();
	work();
	return 0;
}