#include<stdio.h>
#define N 100005
#define M 200005
int *a[N],d[N],x[M],y[M],n,m;
void citire()
{
	freopen("dfs.in","r",stdin);
	freopen("dfs.out","w",stdout);
	scanf("%d%d",&n,&m);
	int s=0;
	for (int i=1; i<=m; ++i)
	{
		scanf("%d%d",&x[i],&y[i]);
		++d[x[i]]; 
		++d[y[i]];
	}
	for (int i=1; i<=n; ++i)
	{
		a[i]= new int [1+d[i]];
		a[i][0]=0;
	}
	for (int i=1; i<=m; ++i)
	{
		a[x[i]][++a[x[i]][0]]=y[i];
		a[y[i]][++a[y[i]][0]]=x[i];
	}
	for (int i=1; i<=n; ++i)
		s+=d[i];
	printf("%d",n-s);
}
int main()
{
	citire();
	return 0;
}