#include<fstream.h>
#define N 100001
typedef struct nod
{long v;
struct nod *leg;}Nod;
typedef struct
{long r;
Nod *l;}head;
head g[N];
long n,m,c[N],i,j,k,t=0,s[N],p;

void add(Nod *&l,long x)
{Nod *p=new Nod;
p->v=x;
p->leg=l;
l=p;}

long del(Nod *&l)
{long x=l->v;
Nod *t=l->leg;
free(l);
l=t;
return x;}

int main()
{ifstream f("dfs.in");
ofstream h("dfs.out");
f>>n>>m;
for(i=1;i<=n;i++)
      g[i].r=0,g[i].l=NULL;
for(k=1;k<=m;k++)
      f>>i>>j,g[i].r++,g[j].r++,add(g[i].l,j),add(g[j].l,i);
for(i=1;i<=n;i++)
if(!c[i])
      {t++,p=1,s[1]=i;
      while(p)
              {k=s[p--],c[k]=1;
              while(g[k].r)
                      {j=del(g[k].l),g[k].r--;
                      if(!c[j])
                                 s[++p]=j;}}}
h<<t;
return 0;}