#include<fstream>
#include<set>
#include<vector>
#include<algorithm>
using namespace std;
ifstream fin("apm.in");
ofstream fout("apm.out");
struct muchie															
{
	int cost;
	int sursa;																
	int dest;																																
};
set<muchie> graf;
vector<int> parinte;
vector<pair<int, int>> sol;
bool operator < (muchie a, muchie b)
{
	if (a.cost == b.cost && a.sursa == b.sursa)
		return a.dest < b.dest;
	else
		if (a.cost == b.cost)
			return a.sursa < b.sursa;
		else
			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 k, x, y, total_cost;
	total_cost = k = 0;
	auto it = graf.begin();
	while (k < n - 1) 
	{
		if (cauta_radacina(it->sursa) != cauta_radacina(it->dest))
		{
			k++;
			total_cost = total_cost + it->cost;
			sol.push_back(make_pair(it->sursa, it->dest));

			uniune(parinte[it->dest], parinte[it->sursa]);
		}
		it++;
	}
	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.insert(muchie{ c,x,y });
	}

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