#include<fstream>
#include<iostream>
#include<vector>
using namespace std;
int p=0,x[100000],n,a,b;
vector<int> v[100000];

void dfs(int i)
{
	for ( vector<int>::iterator it=v[i].begin() ; it!=v[i].end() ; ++it )
	{
		
	 	if(x[*it]==1) dfs(*it);
		x[*it]=0;
		p++;
	}




}

void solve()
{
	for(int i=1;i<=n;++i)
	{
		if(x[i]==1)
			dfs(i);
		
	}
	
}




int main()
{
	int m;
	ifstream f("dfs.in");
	f>>n>>m;
	for(int i=0;i<m;++i)
	{
		f>>a>>b;
		x[a]=1;
		v[a].push_back(b);
	}
	solve();
	ofstream g("dfs.out");
	g<<p;
	return 0;
}