#include<fstream.h>
struct nod{ int inf;
	      nod *leg;}*l[10005];
int s[10005];
unsigned long m,n;
void df(int nod1)
{ 
  s[nod1]=1;
 while(l[nod1])   
 {   
    if(s[l[nod1]->inf]==0)   
      df(l[nod1]->inf);   
   l[nod1]=l[nod1]->leg;   
 }  
 }
int main()
{
 unsigned long nr=0,i,j,k;
 ifstream f("dfs.in");
 f>>n>>m;
 for(k=1;k<=m;k++)
 {
  f>>i>>j;
  nod *p;
  p=new nod;
  p->inf=i;
  p->leg=l[j];
  p=new nod;
  p->inf=j;
  p->leg=l[i];
  l[i]=p;
  }
 df(1);
 for(i=1;i<=n;i++)
{   
 if(s[i]==0){nr++;   
         df(i);   
        }   
 }   
 ofstream g("dfs.out");
 g<<nr;
 return 0;
}