#include <fstream>
#include <vector>
#define MAX 100100

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

void citire();
void DFS(int x);
vector <int> G[MAX];

bool uz[MAX];
int n, m, c;

int main()
{int i;
    citire();
    for(i=1;i<=n;i++)
        if(!uz[i])
    {
        c++;
        DFS(i);
    }
    fout << c;
}

void citire()
{int i, x, y;

    fin >> n >> m;
    for(i=0;i<m;i++)
    {
        fin >> x >> y;
        G[x].push_back(y);

    }
}

void DFS(int x)
{int i;

    //fout << x << ' ';
    uz[x] = 1;
    for(i=0;i<G[x].size();i++)
        if(!uz[G[x][i]])    DFS(G[x][i]);
}