#pragma GCC optimize("O3")
#pragma GCC optimize("unroll-loops")

#include <bits/stdc++.h>
//#define int long long
//#define LL long long
#define double long double
//#define lf Lf
#define fi first
#define se second
#define pb push_back
#define eb emplace_back
#define endl "\n"
#define PII pair<int,int>
#define Gheap priority_queue<int,vector<int>,greater<int>>
#define Lheap priority_queue<int>
#define MAXN 0x3f3f3f3f
#define MINN -0x3f3f3f3f
using namespace std;
//const int N=1e6+100,M=2*N;
//int e[N],w[M],h[M],ne[M],idx;

struct pair_hash
{
    template <class T1, class T2>
    std::size_t operator() (const std::pair<T1, T2> &pair) const
    {
        return std::hash<T1>()(pair.first) ^ std::hash<T2>()(pair.second);
    }
};

unordered_map<int,vector<int>> v;
unordered_map<PII,int,pair_hash> st;
int ans,num;
int n,m;
void dfs(int cur)
{
	if(cur==n and num==1)
	{
		num=0;
		ans++;
		return;
	}

	if(st.size()==m+1) return;

	for(auto z:v[cur])
	{
		//cout<<cur<<' '<<z<<' '<<num<<endl;
		if(!st.contains({cur,z}))
		{
			num=1;
			st[{cur,z}]++;
			dfs(z);
		}
		else 
		{
			st[{cur,z}]++;
			dfs(z);
		}
	}
}
/*
1 3 5
1 2 3 5
1 2 4 5
1 3 4 5
1 2 3 4 5

*/
void solve()
{
	cin>>n>>m;

	for(int i=1;i<=m;i++)
	{
		int a,b;
		cin>>a>>b;
		v[a].pb(b);
	}

	dfs(1);
    cout<<ans<<endl;
}

int main()
{
    std::ios::sync_with_stdio(false);
    cin.tie(0);
    cout.tie(0);
    int tt=1;
    //cin >> tt;
    while(tt--) solve();
}