#include <bits/stdc++.h>

const std::string FILE_NAME = "kruskal";
std::ifstream fin(FILE_NAME + ".in");
std::ofstream fout(FILE_NAME + ".out");

const int NMAX = 105;

int n, m, costMinim;
std::vector<int> x, y, c, index, radacina, rang, apm;

bool cmp(int i, int j) {
    return (c[i] < c[j]);
}

void read() {
    fin >> n >> m;

    x.resize(n + 1);
    y.resize(n + 1);
    c.resize(n + 1);
    index.resize(n  + 1);

    for(int i = 1; i <= m; ++i) {
        fin >> x[i] >> y[i] >> c[i];
    }

    for(int i = 1; i <= m; ++i) {
        index[i] = i;
        radacina[i] = i;
        rang[i] = 1;
    }
}

int find_R(int node) {
    int R;

    // Cautarea radacinii
    for(R = node;
        radacina[R] != R;
        R = radacina[R]);

    // Compresia drumului
    while(node != radacina[node]) {
        int r = radacina[node];
        radacina[node] = R;
        node = r;
    }

    return R;
}

void unite(int node_A, int node_B) {
    if(rang[node_A] > rang[node_B])
        radacina[node_B] = radacina[node_A];
    else
        radacina[node_A] = radacina[node_B];

    if(rang[node_A] == rang[node_B]) ++rang[node_B];
}

void kurskal() {
    std::sort(index.begin(), index.end(), cmp);

    for(int i = 1; i <= m; ++i) {
        if(find_R(x[index[i]]) != find_R(y[index[i]])) {
            unite(find_R(x[index[i]]), find_R(y[index[i]]));
            apm.push_back(index[i]);
            costMinim += c[index[i]];
        }
    }
}

void write() {
    fout << apm.size() << '\n';
    for(int i : apm) {
        fout << x[i] << ' ' << y[i] << '\n';
    }
}

int main() {
    std::ios_base::sync_with_stdio(false);
    fin.tie(nullptr);
    fout.tie(nullptr);

    read();
    kurskal();
    write();

    return 0;
}