#include <bits/stdc++.h>
#include <bits/extc++.h> 
using namespace std;
#define sz(x) (int)(x).size()
#define rep(i, l, r) for (int i = l; i < (r); i++)
#define all(x) begin(x), end(x)

using ll = long long;
using vi = vector<int>;

using pii = pair<int, int>;

struct edge {
    int u, v, w, i;
};

struct DSU {
    int n;
    vector<int> par;

    DSU(int n) : n(n) {
        par = vector<int>(n, -1);
    }


    int leader(int x) {
        if (par[x] < 0) return x;
        return par[x] = leader(par[x]);
    }

    bool same(int x, int y) {
        return leader(x) == leader(y);
    }

    void merge(int x, int y) {
        x = leader(x);
        y = leader(y);
        if (x == y)return;

        par[x] += par[y];
        par[y] = x;
    }
};


int main() {
    int n, m;cin >> n >> m;
    vector<edge> ed(m);
    int t = 0;
    vector<vector<pii>> g(n);
    for (auto &[u, v, w, i] : ed) {
        cin >> u >> v >> w;
        i = t++;
        u--;
        v--;
        g[u].emplace_back(v, i);
        g[v].emplace_back(u, i);
    }

    vector<int> idx(m); iota(all(idx), 0);
    sort(all(idx), [&](int i, int j){
        if (ed[i].w == ed[j].w)return i < j;
        else return ed[i].w < ed[j].w;
    });
    
    vector<int> flag(m, 0);
    DSU dsu(n);
    for (auto i: idx) {
        // cout << ed[i].u << " " << ed[i].v << endl;
        if (dsu.same(ed[i].u, ed[i].v))continue;
        dsu.merge(ed[i].u, ed[i].v);
        flag[i] = 1;
    }
    vector<int> now(m, 0);rep(i, 0, n-1)now[i] = 1;
    // rep(i, 0, m) cout << flag[i] << " ";cout << endl;
    auto dfs = [&](auto self, int v, int p, int target)-> int {
        // cout << v+1 << endl;
        if (target == v) return -1;
        for (auto [u, i]: g[v]) {
            if (now[i] ^ 1)continue;
            if (u == p)continue;
            int x = self(self, u, v, target);
            // cout <<v+1 << " x:" << x << endl;
            if (x >= 0) return x;
            if (x == -1 && flag[i] == 0) return i;
            else if (x == -1) return -1;
        }
        return -2;
    };
    vector<pii> ans;
    rep(i, n-1, m) {
        if (flag[i] ^ 1)continue;
        int x = dfs(dfs, ed[i].u, -1, ed[i].v);
        // cout << x << endl;
        now[x] = 0;
        now[i] = 1;
        ans.emplace_back(i, x);
    }
    cout << sz(ans) << endl;
    for (auto [x, y]: ans) {
        cout << x+1 << " " << y+1 << endl;
    }

    

}