#include<iostream>
#include<cstdio>
#include<cstring>
using namespace std;
long long f[21][1<<20];
int cant[21];
int settle[21];
int top;
int n, m;
long long ans; 
void make_settle() {
	for(int i = 1; i <= n; i++) {
		settle[i] = 1<<(i-1);
		top += settle[i];
	}
}
void read() {
	scanf("%d %d", &n, &m);
	int x, y;
	for(int i = 1; i <= m; i++) {
		scanf("%d %d", &x, &y);
		cant[x] += 1<<(y-1);
	}
} 
bool judge(int num, int tar, int line) {
	if(num & settle[tar]) return false;
	if(cant[line] & settle[tar]) return false;
	return true;
}
void solve() {
	f[0][0] = 1;
	for(int i = 1; i <= n; i++) {
		for(int j = 0; j <= top; j++) {
			if(!f[i-1][j]) continue;
			for(int k = 1; k <= n; k++) {
				if(!judge(j, k, i)) continue;
				f[i][j | settle[k]] += f[i-1][j];
			} 
		}
	}
	for(int i = 0; i <= top; i++) {
		ans += f[n][i];
	}
	printf("%lld", ans);
}
void dfs(int line, int now) {
	if(line == n+1) { ans++; return; }
	for(int i = 1; i <= n; i++) {
		if((cant[line] & settle[i])||(settle[i] & now)) continue;
		dfs(line+1, settle[i] | now);
	}
}
int main() {
	freopen("arrange.in", "r", stdin);
	freopen("arrange.out", "w", stdout);
	read();
	make_settle();
	if(n <= 8) {
		dfs(1, 0);
		printf("%lld\n", ans);
		return 0;
	}
	solve();
	return 0;
}