#include <bits/stdc++.h>
using namespace std;

vector <int> g[100005];
int n,m,x,y;
bool viz[100005]= {false};

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

void DFS(int node)
{
    if(!viz[node])
    {
        viz[node] = true;
        for(int i=0; i<g[node].size(); i++)
        {
            DFS(g[node][i]);
        }
    }
}
int main()
{
    int mp=0;
    f>>n>>m;
    for(int i=1; i<=m; i++)
    {
        f>>x>>y;
        g[x].push_back(y);
    }
    for(int j=1;j<=n; j++){
        if(!viz[j]){
            DFS(j);
            mp++;
        }
    }
    o<<mp<<"\n";
    return 0;
}