#include <iostream>
#include <fstream>
#include <vector>
using namespace std;
ifstream fin("dfs.in");
ofstream fout("dfs.out");
vector <int> v[100005];
int viz[100005],x,y,k,n,m;
void dfs(int nod)
{
    viz[nod]=1;
    for(vector<int>::iterator it=v[nod].begin();it<v[nod].end();it++)
    {
        int nr=*it;
        if(!viz[nr])
        {
            k++;
            dfs(nr);
        }
    }
}
int main()
{
    fin>>n>>m;
    for(int i=1;i<=n;i++)
    {
        fin>>x>>y;
        v[x].push_back(y);
        v[y].push_back(x);
    }
    for(int i=1;i<=n;i++)
        if(!viz[i])
            dfs(i);
    fout<<k<<"\n";
    return 0;
}