#include<iostream>
#include<fstream>
using namespace std;
ifstream f("dfs.in");
ofstream g("dfs.out");
int n, m, viz[100005],c,a[257][257];
struct nod
{
	int info;
	nod* leg;
};
nod *v[100005]; 
void adaug_fata(nod*& p, int x)
{
	nod* r;
	r = new nod;
	r->info = x;
	r->leg = p;
	p = r;

}

void citire()
{
    nod *p = NULL;
	nod *q = NULL;
	f >> n >> m;
	int i, x, y;
	for (i = 1; i <= m; i++)
	{
		f >> x >> y;
		adaug_fata(p, y);
		adaug_fata(p, x);
	}
}

void DFS(int n)
{
	int i;
	viz[n] = 1;
	nod* p;
	for (p=v[n]; p!= NULL; p = p->leg)
		if(viz[p->info]!=0)
		{
			viz[p->info] = 1;
			DFS(p->info);
		}
}
int main()
{
	citire();
	int i;
	for (i = 1; i <= n; i++)
		if (viz[i] == 0)
		{
			c++;
			DFS(i);
		}
	g << c/2;
}