#include<bits/stdc++.h>
#include<cstdio>
#include<iostream> 
#include<cstring>
using namespace std;
const int maxn=50001;
int n,m,a[maxn],b[maxn],ans=0;
int fa[maxn],rank[maxn],root[maxn];
int find(int x){
	if(fa[x]==x)return x;
	return fa[x]=find(fa[x]);
}
void unite(int x,int y){
	x=find(x);
	y=find(y);
	if(x==y)return ;
	if(rank[x]<rank[y]){
		fa[x]=y;
	}
	else{
		fa[y]=x;
		if(rank[x]==rank[y])rank[x]++;
	}
	return ;
}
int main(){
	freopen("religion.in","r",stdin);
	freopen("religion.out","w",stdout);
	scanf("%d%d",&n,&m);
	for(int i=1;i<=n;i++)fa[i]=i;
	for(int i=1;i<=m;i++){
		scanf("%d%d",&a[i],&b[i]);
		unite(a[i],b[i]);
	}
	for(int i=1;i<=n;i++)int t=find(i);
	for(int i=1;i<=n;i++)
	if(!root[fa[i]]){
		//cout<<fa[i]<<endl;
		root[fa[i]]++;
		ans++;
	}
	printf("%d\n",ans);
	return 0;
}