#include<fstream>
#include<iostream>
#include<vector>
#define MMAX 20000002
#define NMAX 100002
using namespace std;
ifstream in("dfs.in");
ofstream out("dfs.out");
vector <int> v[MMAX];
int n,m;
bool viz[NMAX];
void read ()
{

     in>>n>>m;
     int x,y;
     for(int i=1; i<=m; i++)
       {
             in>>x>>y;
              v[x].push_back(y);
              v[y].push_back(x);
       }

}
void dfs(int nod)
{
      viz[nod]=1;
     for(int i=0; i<v[nod].size(); ++i )
                 if(viz[v[nod][i]]==0)
                      dfs(v[nod][i]);
}
 int main ()
 {
     int p=0;
     read();
     dfs(1);
     for(int i=1; i<=n; ++i)
          if(viz[i]==0)
         {
            dfs(i);
            p++;
         }


      out<<p ;
      in.close();
      out.close();
      return 0;

 }