#include <bits/stdc++.h>

using namespace std;

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

#define Nmax 100010

vector<int> v[Nmax];
int viz[Nmax];
int nrComp = 0;

void dfs(int x)
{
	int nrViz = 0;
	viz[x] = 1;
	for(int i = 0; i < v[x].size(); ++i)
    {
        if(viz[v[x][i]] == 0)
        {
            viz[v[x][i]] = 1;
            dfs(v[x][i]);
        }
    }

}


int main()
{
    int n,m,x,y;
    fin >> n >> m;
    for(int i=1; i<=m; i++)
    {
        fin >> x >> y;
        v[x].push_back(y);
    }
    for(int i=1;i<=n;++i) {
	if (viz[i] == 0) // am gasit o componenta conexa noua
    {
        ++nrComp;
        dfs(i);
    }
    }
    fout << nrComp << endl;

    return 0;
}