import java.io.*;
import java.util.Scanner;

class Node {
    public int info;
    public Node next;

    public Node() {
        this.next = null;
        this.info = -1;
    }

    public Node(int info) {
        this.info = info;
        this.next = null;
    }
}

class Problem {
    private String    inputFile ;
    private String    outputFile;
    private Node[]    graph;
    private int       solution;
    private boolean   solved;
    private boolean   wroteSolution;
    private String    fileEncoding;
    private boolean[] marked;

    public Problem(String inputFile, String outputFile) {
        this.inputFile    = inputFile;
        this.outputFile   = outputFile;
        this.solved       = false;
        this.fileEncoding = "UTF-8";
        this.graph        = null;
        this.marked       = null;
        this.readGraph();
    }

    public void solve() {
        int len = this.graph.length;
        this.marked = new boolean[len];
        int cnt = 0;

        for(int i = 1; i < len; ++i) {
            if(!this.marked[i]) {
                this.dfs(i);
                ++cnt;
            }
        }

        this.solution = cnt;
        this.solved = true;
    }

    public int getSolution() {
        if (!this.solved) {
            throw new UnsupportedOperationException();
        }

        return solution;
    }

    public void writeSolutionToFile() {
        if (this.wroteSolution) {
            throw new UnsupportedOperationException();
        }

        try {
            PrintWriter writer = new PrintWriter(this.outputFile, this.fileEncoding);
            writer.println(this.getSolution());
            writer.close();
        } catch (FileNotFoundException | UnsupportedEncodingException e) {
            e.printStackTrace();
        }

        this.wroteSolution = true;
    }

    private void readGraph() {
        if(this.graph == null) {
            try {
                FileReader reader = new FileReader(this.inputFile);
                Scanner input = new Scanner(reader);

                int n = input.nextInt();
                int m = input.nextInt();

                for(this.graph = new Node[n + 1]; m > 0; --m) {
                    int i = input.nextInt();
                    int j = input.nextInt();
                    Node node1 = new Node(j);
                    node1.next = this.graph[i];
                    this.graph[i] = node1;
                    Node node2 = new Node(i);
                    node2.next = this.graph[j];
                    this.graph[j] = node2;
                }
            } catch (IOException var9) {
                var9.printStackTrace();
            }
        }
    }

    private void dfs(int startNode) {
        this.marked[startNode] = true;

        for (Node node = this.graph[startNode]; node != null; node = node.next) {
            if (!this.marked[node.info]) {
                this.dfs(node.info);
            }
        }
    }
}

public class Main {

    public static void main(String[] args) {

        Problem problem = new Problem("dfs.in", "dfs.out");
        problem.solve();
        problem.writeSolutionToFile();
    }
}