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

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

const int NLIM = 100005;
int N, M;
bool vizitat[NLIM];
vector<int> Muchii[NLIM];
int insule = 0;

void DFS(int NOD)
{
    vizitat[NOD] = true;
    for(unsigned int i = 0; i<Muchii[NOD].size();i++){
        int Vecin =Muchii[NOD][i];
        if (!vizitat[Vecin])
            DFS(Vecin);
    }
}

void Citire(){
    fin >> N>>M;
    for (int i = 1; i<= M; i++)
    {
        int x, y;
        fin >> x >> y; // Legatura
        Muchii[x].push_back(y);
        Muchii[y].push_back(x);
    }
    for(int i = 1; i<N; i++)
    {
        if(!vizitat[i])
        insule +=1;{
            DFS[i];
        }
    }
}

int main(){
    Citire();
    fout<<insule<< "\n";
    return 0;

}