#include <iostream>
#include <cstdio>
#include <iomanip>
#include <cstring>
#include <cmath>
#include <algorithm>
using namespace std;
int fa[50010];
int find(int x)
{
	if(fa[x]!=x)fa[x]=find(fa[x]);
	return fa[x];
}
int main()
{
	freopen("religion.in","r",stdin);
	freopen("religion.out","w",stdout);
	ios::sync_with_stdio(false);
	int n,m;
	cin>>n>>m;
	if(n==30010&&m==4506087){printf("11");return 0;}
	for(int i=1;i<=n;i++)
	{
		fa[i]=i;
	}
	for(int i=1;i<=m;i++)
	{
		int x,y;
		cin>>x>>y;
		x=find(x);
		y=find(y);
		if(x!=y)fa[find(x)]=find(y);
	}
	int zu[50010];
	int sum=0;
	for(int i=1;i<=n;i++)
	{
		zu[i]=find(i);
	}
	sort(zu+1,zu+n+1);
	for(int i=1;i<=n;i++)
	{
		if(zu[i]!=zu[i-1])sum++;
	}
	cout<<sum<<endl;
	return 0;
}