#include <fstream>
#include <algorithm>

using namespace std;

struct muchie {
	int cost;
	int a, b;
	bool operator<(const muchie& alt) const {
		return this->cost < alt.cost;
	}
};

const int N = 2e5 + 1, M = 4e5;

int sef[N];
muchie mc[M], rez[N];

int sefsuprem(int nod) {
	if (sef[nod] == nod)
		return nod;
	return sef[nod] = sefsuprem(sef[nod]);
}

bool unire(int a, int b) {
	int sef_a, sef_b;
	sef_a = sefsuprem(a);
	sef_b = sefsuprem(b);
	if (sef_a == sef_b)
		return false;
	sef[sef_a] = sef_b;
	return true;
}

int main() {
	ifstream in("apm.in");
	ofstream out("apm.out");

	int n, m;
	in >> n >> m;
	for (int i = 1; i <= n; ++i)
		sef[i] = i;
	for (int i = 0; i < m; ++i)
		in >> mc[i].a >> mc[i].b >> mc[i].cost;
	sort(mc, mc + m);
	int poz = 0, cost = 0;
	for (int i = 0; i < n - 1; ++i) {
		while (!unire(mc[poz].a, mc[poz].b))
			++poz;
		cost += mc[poz].cost;
		rez[i] = mc[poz];
		++poz;
	}
	out << cost << '\n';
	for (int i = 0; i < n - 1; ++i)
		out << rez[i].a << ' ' << rez[i].b << '\n';

	in.close();
	out.close();
	return 0;
}