#include <bits/stdc++.h>

using namespace std;
ifstream fin("dfs.in");
ofstream fout("dfs.out");

vector <int> v[100100];
bool viz[100100];
int n,m,a,b, nr;
int main()
{
    fin>>n>>m;

    for(int i=1;i<=m;++i)
    {
        fin>>a>>b;
        v[a].push_back(b);
    }

    for(int i=1;i<=n;++i)
    {
        if(viz[i]==false)
        {
            viz[i]=1;
            deque<int> q;
            q.push_back(i);
            int x,y;

            while(q.empty()==false)
            {
                x=q.front();
                q.pop_front();
                for(int j=0;j<v[x].size();++j)
                {
                    y=v[x][j];
                    if(viz[y]==false)
                    {
                        viz[y]=true;
                        q.push_back(y);
                    }
                }
            }

            ++nr;
        }
    }

    fout<<nr;
    return 0;
}