Union-Find

import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;
import java.util.ArrayList;
import java.util.Comparator;
import java.util.PriorityQueue;
import java.util.StringTokenizer;

class Edge implements Comparable, Comparator {
	int s;
	int e;
	int w;

	Edge(int s, int e, int w) {
		this.s = s;
		this.e = e;
		this.w = w;
	}

	@Override
	public int compare(Edge arg0, Edge arg1) {

		if (arg0.w < arg1.w) {
			return -1;
		} else if (arg0.w > arg1.w) {
			return 1;
		}
		return 0;
	}

	@Override
	public int compareTo(Edge arg0) {

		
if (this.w < arg0.w) {l
			return -1;
		} else if (this.w > arg0.w) {
			return 1;
		}
		return 0;
	}
}

public class Main {

	/*
	 * 최소 스패닝 트리 https://vwww.acmicpc.net/problem/11758
	 */
	
	static int[] P;

	public static void main(String[] args) throws IOException {

		//System.setIn(new FileInputStream("res/algo4/F.txt"));
		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
		BufferedWriter bw = new BufferedWriter(new OutputStreamWriter(System.out));

		StringTokenizer ST = new StringTokenizer(br.readLine());
		int V = Integer.parseInt(ST.nextToken());
		int E = Integer.parseInt(ST.nextToken());

		ArrayList A = new ArrayList();
		int a = 0, b = 0, w = 0;
		for (int i = 1; i <= E; i++) {
			ST = new StringTokenizer(br.readLine());

			a = Integer.parseInt(ST.nextToken());
			b = Integer.parseInt(ST.nextToken());
			w = Integer.parseInt(ST.nextToken());
			
			A.add(new Edge(a, b, w));
		}

		// priority 큐 입력
		PriorityQueue pq = new PriorityQueue();
		for (int i = 0; i < E; i++) {
			pq.add(A.get(i));
		}

		P = new int[V + 1];
		for (int i = 1; i <= V; i++){
			P[i] = i;
		}
	
        int result = 0;
		for (int i = 0; i < E; i++){
			Edge node = pq.poll();
			int s = node.s;
			int e = node.e;
			
			int ps = find(s);
			int pe = find(e);
			
			if (ps != pe) {
				union(s, e);
				result += node.w;
			}
		}
		
		
		bw.write(result+"\n");

		br.close();
		bw.flush();
		bw.close();
	}

	static void union(int a, int b) {
		int ua = find(a);
		int ub = find(b);
		
		if (ua == ub) return;
		P[ua] = b;
	}

	static int find(int a) {
		if (P[a] == a) return a;
		return P[a] = find(P[a]);		
	}

}