#include<fstream>
#include<iostream>
#include<vector>
#include<algorithm>
using namespace std;
ifstream fin("apm.in");
ofstream fout("apm.out");
struct muchie															
{
	int sursa;																
	int dest;																
	int cost;																
};
vector<muchie> graf;
vector<int> parinte;
vector<pair<int, int>> sol;

inline bool SortByCost(muchie a, muchie b) { return a.cost < b.cost; }

int cauta_radacina(int x)
{
	if (x == parinte[x])
		return x;
	else
		return parinte[x] = cauta_radacina(parinte[x]);
}


void uniune(int x, int y)
{
	int frunza, radacina;
	frunza = cauta_radacina(x);
	radacina = cauta_radacina(y);
	parinte[frunza] = radacina;
}

void kruskal(int n, int m)
{
	int i, k, x, y, total_cost;
	total_cost = i = k = 0;
	while (k < n - 1) 
	{
		if (cauta_radacina(graf[i].sursa) != cauta_radacina(graf[i].dest))
		{
			k++;
			total_cost = total_cost + graf[i].cost;
			sol.push_back(make_pair(graf[i].sursa, graf[i].dest));

			x = parinte[graf[i].dest];			
			y = parinte[graf[i].sursa];

			uniune(x, y);
		}
		i++;
	}
	fout << total_cost << "\n";
}

int main()
{
	int noduri, muchii, x, y, c;
	fin >> noduri >> muchii;
	for (int i = 0; i <= noduri; i++)
		parinte.push_back(i);

	for (int i = 0; i < muchii; i++)
	{
		fin >> x >> y >> c;
		graf.push_back(muchie{ x,y,c });
	}
	sort(graf.begin(), graf.end(), SortByCost);
	
	kruskal(noduri,muchii);

	fout << sol.size() << "\n";
	for (auto it : sol)
		fout << it.first << " " << it.second << "\n";
	return 0;
}