#include <iostream>
#include <fstream>
#include <vector>

using namespace std;

void dfs(int nod, vector<bool>& vis, vector<vector<int>>& adj){
    for(const auto& v : adj[nod]){
        if(!vis[v]){
            vis[v] = true;
            dfs(v, vis, adj);
        }
    }
}

int main()
{
    ifstream fin ("dfs.in");
    ofstream fout ("dfs.out");
    int n, m;
    fin >> n >> m ;
    vector<vector<int>> adj(n + 1);
    for(int i = 0; i < m; i++){
        int x, y;
        fin >> x >> y;
        adj[x].push_back(y);
        adj[y].push_back(x);
    }
    vector<bool> vis(n + 1, 0);
    vis[1] = true;
    dfs(1, vis, adj);
    int cnt = 1;

    for(int i = 2; i <= n ; i ++){
        if(!vis[i]){
            cnt ++;
            dfs(i, vis, adj);
        }
    }

    fout << cnt;

    fin.close();
    fout.close();

    return 0;
}