#include <algorithm>
#include <cassert>
#include <cstdio>
#include <fstream>
#include <vector>

#define edge pair<int,int>

using namespace std;
vector< pair<int, edge> > Graph, MST;
int nodes, edges, parent[10001];

int findSet(int x, int *parent) {
	if (x != parent[x])
		parent[x] = findSet(parent[x], parent);
	return parent[x];
}

int main() {
	ifstream fin("input.txt"); assert( fin );
	fin >> nodes >> edges;
	
	// controllo input
	if (!( nodes >= 1 && nodes <= 10000 && edges >= 2 && edges <= 1000000 )) return 1;
	
	// inizializzo
	for (int i = 1; i <= nodes; i++) parent[i] = i;
	MST.clear();
	Graph.clear();
	
	// popolo il grafo
	int u, v, w;
	for (int i = 0; i < edges; i++) {
		fin >> u >> v >> w;
		Graph.push_back( pair<int, edge>(w, edge(u,v)) );
	}
	
	// eseguo Kruskal
	sort( Graph.begin(), Graph.end() );
	int totalWeight = 0;
	for (int i = 0; i < edges; i++) {
		int pu = findSet(Graph[i].second.first, parent);
		int pv = findSet(Graph[i].second.second, parent);
		if (pu != pv) {
			totalWeight += Graph[i].first;
			MST.push_back(Graph[i]);
			parent[pu] = parent[pv];
		}
	}
		
	ofstream fout("output.txt"); assert( fout );
	fout << totalWeight << endl;
	for (int i = 0; i < MST.size(); i++)
		fout << MST[i].second.first << " " << MST[i].second.second << endl;
	fout.close();
	return 0;
}