#include <algorithm>
#include <iostream>
#include <vector>
#include <fstream>

using namespace std;

struct Muchie {
    int x, y, c;

    bool operator<(const Muchie &m) const {
        return c < m.c;
    }
};

const int MAX = 400000;
vector<Muchie> M;
vector<pair<int, int> > APCM;
int tata[MAX + 1], h[MAX + 1];

void Initialize(int u) {
    tata[u] = 0;
    h[u] = 0;
}

int Find(int u) {
    if (tata[u] == 0) {
        return u;
    }
    return tata[u] = Find(tata[u]);
}

void Union(int u, int v) {
    int ru = Find(u);
    int rv = Find(v);
    if (h[ru] > h[rv]) {
        tata[rv] = ru;
    } else {
        tata[ru] = rv;
        if (h[ru] == h[rv]) {
            h[rv]++;
        }
    }
}

int main() {
    ifstream fin("apm.in");
    ofstream fout("apm.out");
    int n, m, cost = 0;
    fin >> n >> m;
    for (int i = 1; i <= m; i++) {
        int x, y, c;
        fin >> x >> y >> c;
        M.push_back({x, y, c});
    }
    sort(M.begin(), M.end());
    for (int i = 1; i <= n; i++) {
        Initialize(i);
    }
    for (const auto &muchie: M) {
        if (Find(muchie.x) != Find(muchie.y)) {
            cost += muchie.c;
            Union(muchie.x, muchie.y);
            APCM.push_back({muchie.x, muchie.y});
            if (APCM.size() == n - 1) {
                break;
            }
        }
    }
    fout << cost << "\n";
    for (const auto &muchie: APCM) {
        fout << muchie.first << " " << muchie.second << "\n";
    }

    return 0;
}