J11724_6.java

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.ArrayList;
import java.util.LinkedList;

public class J11724_6 {
 static int n, m;
 static LinkedList<Integer>[] list;
 static boolean visited[];
 public static void main(String[] args) throws IOException {
 BufferedReader buffer = new BufferedReader(new InputStreamReader(System.in));

 String[] input = buffer.readLine().split(" ");

 n = Integer.parseInt(input[0]);
 m = Integer.parseInt(input[1]);

 list = new LinkedList[n+1];

 for(int i = 0 ; i <= n; i++){
 list[i] = new LinkedList<>();
 }
 visited = new boolean[n+1];
 for(int i = 0 ; i < m; i++){
 input = buffer.readLine().split(" ");
 int start = Integer.parseInt(input[0]);
 int end = Integer.parseInt(input[1]);

 list[start].add(end);
 list[end].add(start);
 }
 int cnt = 0;
 for(int i =1 ; i<= n; i++){

 if(!visited[i]){
 dfs(i);
 cnt++;
 }
 }

 System.out.println(cnt);
 }
 public static void dfs(int a){
// if(visited[a]) return;
 visited[a] = true;
 for(int next : list[a]){
 if(!visited[next]){
 dfs(next);
 }
 }
 }
}