#include<fstream>
#include<cstring>
using namespace std;
int k,a[1001][1001],viz[1001];
int n,m,i,x,y;
void dfs(int x)
{
	viz[x]=1;
	for(i=1;i<=n;i++) if((viz[i]==0)&&(a[x][i]==0)) dfs(i);
}
int main()
{
	ifstream fi("dfs.in");
	ofstream fo("dfs.out");
	fi>>n>>m;
	memset(a,0,sizeof(a));
	for(i=1;i<=m;i++)
	{
		fi>>x>>y;
		a[x][y]=a[y][x]=1;

	}
	k=0;
	memset(viz,0,sizeof(viz));
	for(i=1;i<=n;i++) if(viz[i]==0) {k++; dfs(i); }
	fo<<k<<"\n";
	fo.close();

}