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

std::ifstream fin("dfs.in");
std::ofstream fout("dfs.out");

class Node 
{
    int value;
    Node* next;
public:
    Node(int x = 0, Node* adr = nullptr) : value(x), next(adr) {}

    void set_value(int value) { this->value = value; }
    void set_next(Node* next) { this->next = next; }

    Node* get_next() { return next; }
    int get_value() { return value; }

    Node& operator= (const Node& altul)
    {
        this->next = altul.next;
        this->value = altul.value;
        return *this;
    }

};



void create_connection(std::vector <Node>& v, int head, int tail)
{
    Node* A = new Node();
    A->set_value(tail);
    A->set_next(v[head].get_next());
    v[head].set_next(A);
}

void DFS(std::vector <Node>& lista, int (&descoperit)[], int x, int &comp_conexe)
{
    descoperit[x] = comp_conexe;
    Node* A = &(lista[x]);
    while (A->get_next() != nullptr)
    {
        A->set_value(A->get_next()->get_value()); 
        A->set_next(A->get_next()->get_next());
        int val = A->get_value();
        if (descoperit[val] == 0)
            DFS(lista, descoperit, val, comp_conexe);
        
    } 
    

}

int main()
{
    std::vector < Node > lista ;
    int n, m, x , y;
    
    fin >> n >> m;
    
    lista.resize(n+1);
    for (int i = 0; i <= n; i++)
        lista[i].set_value(i);
    
    for (int count = 1; count <= m; ++count)
    {
        fin >> x >> y;

        create_connection(lista, x, y);

        create_connection(lista, y, x);     
    }
    
    int descoperit[n+1] = { 0 };

    int nod, comp_conexe = 0;
    bool gata = false;
    
    while(gata == false)
    {
        gata = true;
        for (int i = 1; i <= n && gata; ++i)
            if (descoperit[i] == 0)
                { gata = false; nod = i; }
        if (!gata)
        {
            comp_conexe++;
            DFS(lista, descoperit, nod, comp_conexe);
        }
        
    }

    fout << comp_conexe;

}