#include <bits/stdc++.h>

using namespace std;

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

bool viz[100041];
int n, m;
vector <int> g[100041];

void read()
{
    fin >> n >> m;
    for (int i=0;i<m;++i)
    {
        int x, y;
        fin >> x >> y;
        g[x].push_back(y);
    }
}

void dfs(int st)
{
    viz[st]=true;
    for (int i=0;i<g[st].size();++i)
    {
        if (!viz[g[st][i]])
        {
            dfs(g[st][i]);
        }
    }
    return;
}

int main()
{
    read();
    int c=0;
    for (int i=1;i<=n;++i)
    {
        if (!viz[i])
        {
            dfs(i);
            c++;
        }
    }
    fout << c;
    return 0;
}