#include <bits/stdc++.h>
#include <atcoder/all>
using namespace std;
using ll = long long;
#define rep(i,n) for(int i=0;i<(int)(n);i++)

int main(){
	int n,m;
	cin>>n>>m;
	vector<int> in(n,0),ou(n,0);
	atcoder::dsu uf(n);
	rep(i,m){
		int u,v;
		cin>>u>>v;
		u--; v--;
		ou.at(u)++;
		in.at(v)++;
		uf.merge(u,v);
	}
	map<int,int> mp;
	rep(i,n){
		if(in.at(i)>ou.at(i)) mp[uf.leader(i)]+=in.at(i)-ou.at(i);
		mp[uf.leader(i)];
	}
	ll ans=0;
	for(auto [ld,nm]:mp){
		if(in.at(ld)==0&&ou.at(ld)==0){
			continue;
		}
		if(nm>0) ans+=nm-1;
		ans++;
	}
	if(ans>0) ans--;
	cout<<ans<<endl;
}