#include<iostream>
#include<stdio.h>
#include<stack>
using namespace std;
struct nod {int inf;nod *next;} *a[100010],*p;
stack<int> st;
int n,m,i,ut[100010],nr,x,y;
int main()
{
	freopen("dfs.in","r",stdin);
	freopen("dfs.out","w",stdout);
	scanf("%d%d",&n,&m);
	for(i=1;i<=m;i++)
	{
		scanf("%d%d",&x,&y);
		p=new nod; p->next=a[x];p->inf=y;a[x]=p;
		p=new nod; p->next=a[y];p->inf=x;a[y]=p;
	}
	for(i=1;i<=n;i++)
		if(!ut[i])
		{
			nr++;
			st.push(i);
			while(!st.empty())
			{
				for(p=a[st.top()];p;p=p->next)
					if(!ut[p->inf])
						st.push(p->inf);
				if(!ut[st.top()])
					ut[st.top()]=1;
				else
					st.pop();
			}
		}
	printf("%d\n",nr);
	return 0;
}