#include <fstream>
#include <vector>
#include <algorithm>

using namespace std;

ifstream cin("dfs.in");
ofstream cout("dfs.out");

vector <vector <int> > a;
vector <bool> v;
vector <int> c;

void read()
{
    int n,m,x,y;
    cin >> n >> m;
    a.resize(n+1);
    for ( ; m ; m--)
    {
        cin >> x >> y;
        if (x!=y)
        {
            a[x].push_back(y);
            a[y].push_back(x);
        }
    }
    v.resize(n+1);
}

void solve()
{
    int mx=0,cs;
    vector <bool> p(a.size());
    for (int i=1; i<v.size(); i++)
    {
        c.clear();
        if (a[i].size()==0 && !v[i])
        {
            v[i]=true;
            mx++;
        }
        if (!v[i])
        {
            c.push_back(i);
            fill(p.begin(),p.end(),false);
            p[i]=true;
            for (int j=0; j<c.size(); j++)
            {
                for (int z=0; z<a[c[j]].size(); z++)
                    if (!p[a[c[j]][z]])
                    {
                        c.push_back(a[c[j]][z]);
                        v[a[c[j]][z]]=true;
                        p[a[c[j]][z]]=true;
                    }
            }
            mx++;
        }
    }
    cout << mx;
}

main()
{
    read();
    solve();
}