#include<iostream>
#include<algorithm>
#include<cmath>
#include<cstring>
#include<cstdio>
#include<vector>
using namespace std;
vector<int>b[100010];
int n,m,a1,a2,r[100010];
long long f[100010],ans=0;
bool bk[100010];
inline void dfs(int p){
	bk[p]=1;
	if(!b[p].size())return;
    for(int i=0;i<b[p].size();i++)f[b[p][i]]+=f[p],r[b[p][i]]--;
	for(int i=0;i<b[p].size();i++)if(!r[b[p][i]]&&!bk[b[p][i]])dfs(b[p][i]);
    return;
}
int main(){
	freopen("chain_2016.in","r",stdin);
    freopen("chain_2016.out","w",stdout);
	scanf("%d%d",&n,&m);
	if(m)for(int i=1;i<=m;i++){
	    scanf("%d%d",&a1,&a2);
		b[a1].push_back(a2);
		r[a2]++;
	}
	for(int i=1;i<=n;i++)if(r[i]==0&&!bk[i]){
		if(!b[i].size())continue;
	    f[i]=1,dfs(i);
    }
	for(int i=1;i<=n;i++)if(!b[i].size())ans+=f[i];
	printf("%lld",ans);
	return 0;
}