#include <vector>
#include<fstream>
using namespace std;
#define NMAX 100001

vector<vector<int>> graph(NMAX);
int n, m;
void readFromFile(){
    ifstream fin("dfs.in");
    fin>>n>>m;
    for(int x, y, i=1; i<=m; i++){
        fin>>x>>y;
        graph.at(x).push_back(y);
    }
    fin.close();
}
vector<bool> visited(NMAX, false);

void dfs(int x){
    visited.at(x) = true;
    for(auto& elem:graph.at(x)){
        if(!visited.at(elem)) dfs(elem);
    }
}
int main()
{
    readFromFile();
    int nr = 0;
    for(int i=1; i<=n; i++){
        if(!visited.at(i)){
            nr++;
            dfs(i);
        }
    }
    ofstream fout("dfs.out");
    fout<<nr;
}