#include <fstream>
#include <iostream>
#include <vector>
#include <bitset>
#include <string.h>
#include <algorithm>
#include <iomanip>
#include <math.h>
#include <time.h>
#include <stdlib.h>
#include <set>
#include <map>
#include <string>
#include <queue>
#include <deque>

using namespace std;

const char infile[] = "dfs.in";
const char outfile[] = "dfs.out";

ifstream fin(infile);
ofstream fout(outfile);

const int MAXN = 100005;
const int oo = 0x3f3f3f3f;

typedef vector<int> Graph[MAXN];
typedef vector<int> :: iterator It;

const inline int min(const int &a, const int &b) { if( a > b ) return b;   return a; }
const inline int max(const int &a, const int &b) { if( a < b ) return b;   return a; }
const inline void Get_min(int &a, const int b)    { if( a > b ) a = b; }
const inline void Get_max(int &a, const int b)    { if( a < b ) a = b; }

class DirectedGraph {
private:
    vector <vector <int> > G;
public:
    DirectedGraph() {
    }
    DirectedGraph(int _N) {
        G.resize(_N);
    }
    void addDirectedEdge(int x, int y) {
        G[x].push_back(y);
    }
    void addUndirectedEdge(int x, int y) {
        G[x].push_back(y);
        G[y].push_back(x);
    }
    void dfs(int node, vector <bool>& used) {
        used[node] = 1;
        for(auto it: G[node])
            if(!used[it])
                dfs(it, used);
    }
    int getConnectedComponents() {
        int ans = 0;
        vector <bool> used(G.size(), 0);
        for(int i = 0 ; i < G.size() ; ++ i)
            if(!used[i]) {
                ++ ans;
                dfs(i, used);
            }
        return ans;
    }
    vector <int> bfs(int Source) {
        vector <int> dist(G.size(), -1);
        queue <int> Q;
        Q.push(Source);
        dist[Source] = 0;
        while(!Q.empty()) {
            int node = Q.front();
            Q.pop();
            for(auto it: G[node])
                if(dist[it] == -1) {
                    dist[it] = dist[node] + 1;
                    Q.push(it);
                }
        }
        return dist;
    }
};

int N, M, Source;

int main() {
    fin >> N >> M;
    DirectedGraph G(N);
    for( ; M -- ; ) {
        int x, y;
        fin >> x >> y;
        -- x ; -- y;
        G.addUndirectedEdge(x, y);
    }
    fout << G.getConnectedComponents() << '\n';
    fin.close();
    fout.close();
    return 0;
}