#include <fstream>
#include <vector>
#include <queue>
using namespace std;

ifstream f("dfs.in");
ofstream g("dfs.out");

vector<int> graf[100005];
queue<int> Q;
int l[100005], n, m;

void citire()
{
    int x, y;
    f>>n>>m;
    for(int i = 0; i<m; ++i)
    {
        f>>x>>y;
        graf[x].push_back(y);
    }
}

void parcDfs(int nod)
{
    for(auto &v : graf[nod])
    {
        if(l[v] == 0)
        {
            l[v] = 1;
            parcDfs(v);
        }
    }
}

int main() {
    citire();
    int nr = 0;
    for(int i = 1; i<=n; i++)
    {
        if(l[i] == 0)
        {
            nr++;
            l[i] = 1;
            parcDfs(i);
        }
    }
    g<<nr;
    return 0;
}