#include<fstream>
#include<vector>
#define Nmax 100010
using namespace std;

vector <int> muchii[Nmax];
int st[Nmax], viz[Nmax], k, i, n, m, x, y, ok1, ok, v, j, nr;

void dfs (int x)
{
	st[1]=x;
	viz[x]=1;
	k=1;
	while (k>0)
	{
		y=0;
		v=st[k];
		for (i=1; i<=n; ++i)
			for (j=0; j<muchii[v].size(); ++j)
				if (muchii[v][j]==i && viz[i]==0)
				{
					y=i;
					break;
				}
		if (y==0)
			k--;
		else
		{
			viz[y]=1;
			st[++k]=y;
		}
	}
}

int main()
{
	ifstream f("dfs.in");
	ofstream h("dfs.out");
	f>>n>>m;
	for (i=1; i<=m; ++i)
	{
		f>>x>>y;
		muchii[x].push_back(y);
		muchii[y].push_back(x);
	}
	nr=0;
	ok=0;
	while (ok==0)
	{
		ok1=1;
		for (i=1; i<=n; ++i)
			if (viz[i]==0)
			{
				ok1=0;
				dfs(i);
				nr++;
			}
		if (ok1==1)
			ok=1;
	}
	h<<nr<<'\n';
	return 0;
}