#include <vector>
#include <fstream>

using namespace std;
ifstream cin("dfs.in");
ofstream cout("dfs.out");

vector <int> v[100001];
int n,m,i,viz[100001];
int sol,x,y;
void dfs(int nod)
{

    viz[nod]=1;
    for(int i=0;i<v[nod].size();++i)
    {
        if(!viz[v[nod][i]])
            dfs(v[nod][i]);

    }
}

int main()
{
    cin>>n>>m;
    for(i=1;i<=m;++i)
    {
        cin>>x>>y;
        v[x].push_back(y);
    }


    for(i=1;i<=n;++i)
    {
        if(viz[i]==0)
        {
            dfs(i);
            ++sol;
        }
    }

    cout<<sol;

    return 0;
}