#include <iostream>
#include <fstream>
#include <vector>
#define Nmax 100005
using namespace std;

ifstream reed("DFS.in");
ofstream shaw("DFS.out");

vector <int> v[Nmax];
int a,b,n,m,viz[Nmax],c=0;
void DFS(int nod)
{
  viz[nod]=1;
  for(int i=0;i<v[nod].size();i=i+1){
    if(!viz[v[nod][i]]){
      c++;
      DFS(i);
    }
  }
}

int main()
{
    reed>>n>>m;
    for(int i=1;i<=m;i=i+1){
      cin>>a>>b;
      v[a].push_back(b);
      v[b].push_back(a);
    }
    for(int i=1;i<=n;i=i+1){
      if(!viz[i]){
        DFS(i);
      }
    }
    cout<<c;

    return 0;
}