#include <iostream>
#include <fstream>
#include <queue>
#include <vector>
using namespace std;
const int NMAX=100001;
vector< int > g[NMAX];
queue< int> q;
int vis[NMAX], cc=0;

void dfs(int node)
{
    vis[node]=1;
    for(int i=0; i<g[node].size(); i++)
        if(!vis[g[node][i]])
        {
            vis[g[node][i]]=1;
            dfs(g[node][i]);
        }
}


int main()
{
    ifstream cin("dfs.in");
    ofstream cout("dfs.out");
    int n, m;
    cin>>n>>m;
    for(int i=1; i<=m; i++)
    {
        int u, v;
        cin>>u>>v;
        g[u].push_back(v);
    }

    for(int i=1; i<=n; i++)
        if(!vis[i])
        {
            cc++;
            dfs(i);
        }
    cout<<cc<<'\n';
    return 0;
}