#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;
};
muchie *graf[400001];
int *parinte[200001];
muchie* sol[200000];

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))
		{
			total_cost = total_cost + graf[i]->cost;
			sol[k++]=graf[i];

			uniune(*parinte[graf[i]->dest], *parinte[graf[i]->sursa]);
		}
		i++;
	}
	fout << total_cost << "\n";
}

int main()
{
	int noduri, muchii, x, y, c;
	fin >> noduri >> muchii;
	for (int i = 0; i <= noduri; i++)
		parinte[i] = new int(i);
	parinte[noduri + 1] = nullptr;
	for (int i = 0; i < muchii; i++)
	{
		fin >> x >> y >> c;
		graf[i] = new muchie{ x,y,c };
	}
	graf[muchii] = nullptr;
	sort(graf, graf + muchii, SortByCost);

	kruskal(noduri, muchii);

	fout << noduri - 1 << "\n";
	for (int i = 0; i< noduri - 1; i++)
		fout << sol[i]->sursa << " " << sol[i]->dest << "\n";
	return 0;
}