#include<fstream>
#include<vector>
std :: ifstream in("dfs.in");
std :: ofstream out("dfs.out");
using namespace std;
const int N=1e5+1;
vector<int>a[N];
bool viz[N];
void dfs(int x)
{
    viz[x]=true;
    for(auto y:a[x]) if(!viz[y]) dfs(y);
}
int main()
{
    int n , m;
    in>>n>>m;
    for(int i=0;i<m;i++)
    {
        int x ,y;
        in>>x>>y;
        a[x].push_back(y);
        a[y].push_back(x);
    }
    dfs(1);
    int x=0;
    for(int i=0;i<=n;i++)
    {
        if(!viz[i])
            {
                x++;
                dfs(i);
            }
    }
    out<<x;
}