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package class16;
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// 课上没讲这个实现
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// 因为是一样的，都是用Prim算法实现最小生成树，只不过是牛客网的测试数据
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// 测试链接 : https://www.nowcoder.com/questionTerminal/c23eab7bb39748b6b224a8a3afbe396b
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// 请同学们务必参考如下代码中关于输入、输出的处理
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// 这是输入输出处理效率很高的写法
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// 提交以下所有代码，把主类名改成Main，可以直接通过
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import java.io.BufferedReader;
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import java.io.IOException;
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import java.io.InputStreamReader;
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import java.io.OutputStreamWriter;
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import java.io.PrintWriter;
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import java.io.StreamTokenizer;
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import java.util.ArrayList;
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import java.util.PriorityQueue;
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public class Code05_PrimNowCoder {
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public static void main(String[] args) throws IOException {
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BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
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StreamTokenizer in = new StreamTokenizer(br);
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PrintWriter out = new PrintWriter(new OutputStreamWriter(System.out));
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while (in.nextToken() != StreamTokenizer.TT_EOF) {
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ArrayList<ArrayList<int[]>> graph = new ArrayList<>();
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int n = (int) in.nval;
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for (int i = 0; i <= n; i++) {
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graph.add(new ArrayList<>());
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}
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in.nextToken();
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int m = (int) in.nval;
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for (int i = 0; i < m; i++) {
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in.nextToken();
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int A = (int) in.nval;
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in.nextToken();
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int B = (int) in.nval;
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in.nextToken();
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int cost = (int) in.nval;
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graph.get(A).add(new int[] { B, cost });
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graph.get(B).add(new int[] { A, cost });
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}
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PriorityQueue<int[]> heap = new PriorityQueue<>((a, b) -> a[1] - b[1]);
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boolean[] visited = new boolean[n + 1];
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for (int[] edge : graph.get(1)) {
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heap.add(edge);
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}
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visited[1] = true;
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int ans = 0;
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while (!heap.isEmpty()) {
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int[] edge = heap.poll();
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int next = edge[0];
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int cost = edge[1];
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if (!visited[next]) {
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visited[next] = true;
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ans += cost;
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for (int[] e : graph.get(next)) {
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heap.add(e);
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}
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}
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}
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out.println(ans);
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out.flush();
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}
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}
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}
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