#include <iostream>
#include<fstream>
#include <vector>

using namespace std;
ifstream fin("dfs.in");
ofstream fout("dfs.out");
const int N = 100001;
vector<vector<int>> G(N + 1);
int n, m;

void citire() {
    fin >> n >> m;
    int x, y;
    for (int i = 1; i <= n; i++) {
        fin >> x >> y;
        G[x].push_back(y);
    }
}

void dfs(int x, vector<bool> &viz) {
    viz[x] = true;
    for (auto vecin:G[x])
        if (!viz[vecin]) dfs(vecin, viz);
}

int nrComp() {
    citire();
    int comp = 0;
    vector<bool> viz(n, false);
    for (int i = 1; i <= n; i++)
        if (!viz[i]) {
            comp++;
            dfs(i, viz);
        }
    return comp;
}

int main() {
    fout << nrComp();
    return 0;
}