#include <iostream>

#include <cstring>

using namespace std;

const int VERTEX_NUM = 20;

const int INFINITY = 0x7fffffff;

bool vis[VERTEX_NUM];

int dist[VERTEX_NUM];

int pre[VERTEX_NUM];

class Graph {

public:

	int vexNum;

	int edgeNum;

	int vex[VERTEX_NUM];

	int arc[VERTEX_NUM][VERTEX_NUM];

};

void createGraph(Graph &G)

{

	cout << "please input vexNum and edgeNum: ";

	cin >> G.vexNum >> G.edgeNum;

	for (int i = 0; i != G.vexNum; ++i) {

		cout << "please input no" << i+1 << " vertex: ";

		cin >>  G.vex[i];					// 自定义顶点序号

	}

	for (int i = 0; i != G.vexNum; ++i) {

		for (int j = 0; j != G.vexNum; ++j) {

			G.arc[i][j] = INFINITY;

		}

	}

	for (int k = 0; k != G.edgeNum; ++k) {

		cout << "please input the vertex of edge(vi, vj) and weight: ";

		int i, j, w;

		cin >> i >> j >> w;

		G.arc[i][j] = w;

		G.arc[j][i] = G.arc[i][j];

	}

}

void prim(Graph &G, int src)

{

	memset(dist, INFINITY, VERTEX_NUM);

	memset(vis, false, true);

	for (int i = 0; i != G.vexNum; ++i) {

		pre[i] = src;

		dist[i] = G.arc[src][i];

	}

	vis[src] = true;

	int lowcost;

	int lowcostIndex;

	for (int cnt = 1; cnt != G.vexNum; ++cnt) {

		lowcost = INFINITY;

		for (int i = 0; i != G.vexNum; ++i) {

			if (dist[i] < lowcost && !vis[i]) {

				lowcost = dist[i];		// 没意义，最小生成树考虑的是到生成树而不是源点

				lowcostIndex = i;

			}

		}

		vis[lowcostIndex] = true;

		for (int i = 0; i != G.vexNum; ++i) {

			if (G.arc[lowcostIndex][i] != INFINITY && G.arc[lowcostIndex][i] < dist[i] && !vis[i])

				dist[i] = G.arc[lowcostIndex][i];

				pre[i] = lowcostIndex;

		}

	}

}

int main()

{

	Graph G;

	createGraph(G);

	int src = 0;

	prim(G, src);

	int sum = 0;

	for (int i = 0; i != G.vexNum; ++i) {

		if (src == i) continue;

		sum += dist[i];

	}

	cout << sum << endl;

}