#include<cstdio>
#include<vector>
using namespace std;
#define mata vector<int>
int n,m;
mata v[100002];
void list(void){
	int i,x,y;
	for(i=0;i<m;++i){
		scanf("%d%d",&x,&y);
		v[x].push_back(y); v[y].push_back(x);
	}
}
bool found(int where,int tofind){
	mata::iterator it;
	for(it=v[where].begin();it!=v[where].end();++it)
		if(*it==tofind) return 1;
	return 0;
}
void df(int nod,int viz[]){
	int i;
	viz[nod]=1;
	for(i=1;i<n;++i)
		if(!viz[i]&&found(nod,i)) df(i,viz);
}
int main(){
	int i,viz[100002]={0},cont=0;
	freopen("dfs.in","r",stdin);
	freopen("dfs.out","w",stdout);
	scanf("%d%d",&n,&m);
	list();
	for(i=1;i<=n;++i)
		if(!viz[i]){
			df(i,viz);
			++cont;
		}
	printf("%d\n",cont);
	return 0;
}