#include <iostream>
#include <fstream>
#include <vector>
#include <queue>
#define MAX 100005
using namespace std;
ifstream fin("dfs.in");
ofstream fout("dfs.out");
int n,m;
queue <int> coada;
vector <int> muchii[MAX];
bool viz[MAX];
void citire()
{
    fin>>n>>m;
    bool viz[n+5];
    for(int i=1;i<=m;i++)
    {
        int a,b;
        fin>>a>>b;

        muchii[a].push_back(b);
        muchii[b].push_back(a);
    }
    for(int i=1;i<=n;i++)
    {
        viz[i]=false;
    }

    coada.push(1);
}

void dfs(int nod)
{
    viz[nod]=true;
    coada.pop();
    for(size_t i=0;i<muchii[nod].size();i++)
    {
        int nod_vecin=muchii[nod][i];

        if(viz[nod_vecin]==false)
        {
            coada.push(nod_vecin);
        }
    }

    if(!coada.empty())
    {
        dfs(coada.front());
    }
}

int main()
{
    citire();
    int insule=0;
    for(int i=1;i<=n;i++)
    {
        if(viz[i]==false)
        {
            insule++;
            dfs(i);
        }
    }

    fout<<insule;

    return 0;
}