#include<bits/stdc++.h>

using namespace std;

#define int long long

int const maxn = 2005;
int cmp[maxn], color[maxn];
set < int > g[maxn];

void calc(int v, int p, int c) {
    color[v] = c;
    for (auto u : g[v]) {
        if (u != p) calc(u, v, c);
    }
}

int get(int v) {
    if (cmp[v] == v) return v;
    cmp[v] = get(cmp[v]);
    return cmp[v];
}

main() {
#ifdef HOME
    freopen("input.txt", "r", stdin);
#endif // HOME
    ios_base::sync_with_stdio(0);
    cin.tie(0);
    cout.tie(0);
    int n, m, u, v, w;
    cin >> n >> m;
    vector < vector < int > > Q;
    vector < vector < int > > edges = {{}};
    for (int i = 1; i <= m; i++) {
        cin >> u >> v >> w;
        if (i < n) {
            g[u].insert(v);
            g[v].insert(u);
        }
        edges.push_back({u, v, w});
        Q.push_back({w, i, u, v});
    }
    sort(Q.begin(), Q.end());
    vector < pair < int, int > > ans;
    set < int > ind;
    vector < int > add;
    for (int i = 1; i <= n; i++) cmp[i] = i;
    for (auto key : Q) {
        u = get(key[2]), v = get(key[3]);
        if (u != v) {
            cmp[u] = v;
            if (key[1] >= n) add.push_back(key[1]);
            ind.insert(key[1]);
        }
    }
    //cout << add.size() << endl;
    for (int i = 1; i <= n - 1; i++) {
        if (ind.find(i) == ind.end()) {
            u = edges[i][0], v = edges[i][1];
            calc(u, v, 1), calc(v, u, 2);
            for (auto key : add) {
                int x = edges[key][0], y = edges[key][1];
                if (color[x] != color[y]) {
                    ans.push_back({i, key});
                    g[u].erase(v), g[v].erase(u), g[x].insert(y), g[y].insert(x);
                    break;
                }
            }
        }
    }
    cout << ans.size() << '\n';
    for (auto key : ans) cout << key.first << " " << key.second << '\n';
    return 0;
}