#include<iostream>
#include<cstdio>
#include<cstring>
using namespace std;
const int MAXN=20+1;
int n,m,posl[MAXN],posc[MAXN];
bool map[MAXN][MAXN],b[MAXN][MAXN];
unsigned long long ans;
void dfs(int l=1){//当前行数 
		for(int i=1;i<=n;i++) if(!map[l][i]&&!b[l][i]) {
			if(l+1>n) {
				ans++;
				continue;
			}
			for(int j=l;j<=n;j++) b[j][i]=1;
			dfs(l+1);
			for(int j=l;j<=n;j++) b[j][i]=0;
		}
}
int main(){
	freopen("arrange.in","r",stdin);
	freopen("arrange.out","w",stdout);
	cin>>n>>m;
	int a,b;
	while(m--) cin>>a>>b,map[a][b]=1;
	dfs();
	cout<<ans;
}