#include<iostream>
#include<vector>
#include<cassert>
using namespace std;
int N,M;
bool vis[2<<17];
int deg[2<<17];
vector<int>G[2<<17];
int dfs(int u)
{
	vis[u]=true;
	int ret=max(deg[u],0);
	for(int v:G[u])if(!vis[v])ret+=dfs(v);
	return ret;
}
int main()
{
	cin>>N>>M;
	for(int i=0;i<M;i++)
	{
		int u,v;cin>>u>>v;
		u--,v--;
		G[u].push_back(v);
		G[v].push_back(u);
		deg[u]++;
		deg[v]--;
	}
	int ans=0,zero=0,one=0;
	for(int i=0;i<N;i++)if(!vis[i]&&!G[i].empty())
	{
		int r=dfs(i);
		if(r==0)zero++;
		else
		{
			ans+=r-1;
			one++;
		}
	}
	ans+=zero+one;
	cout<<ans-!!ans<<endl;
}