#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using ld = long double;

#define pb push_back

const ld pi = 3.14159265358979323846;
// const int mod = 998244353;
const ll INF = 1e18;

template<typename T>
T chmax(T a, T b) {
    return a > b ? a : b;
}

template<typename T>
T chmin(T a, T b) {
    return a > b ? b : a;
}

const int N = (int)2e5 + 1, M = N * 2;

struct DSU{
    vector<int> node, size;
 
    DSU(){}
    DSU(int n){
        init(n);
    }
 
    void init(int n){
        node.resize(n);
        size.resize(n);
 
        for(int i = 0; i < n; i++){
            node[i] = i;
            size[i] = 1;
        }
    }
 
    int find(int x){
        return x == node[x] ? x : node[x] = find(node[x]);
    }
 
    void erase(int x){
        size[find(x)] -= 1;
        node[x] = x;
    }
 
    void relocate(int x, int y){ //can't be root
        int dx = find(x), dy = find(y);
        if(dx == dy){
            return;
        }
        node[x] = dy;
        size[dx] -= 1;
        size[dy] += 1;
    }
 
    int set(int x, int y){
        return find(x) == find(y);
    }
 
    int merge(int x, int y){
        x = find(x);
        y = find(y);
        if(x == y){
            return 0;
        }
 
        size[x] += size[y];
        node[y] = x;
        return 1;
    }
 
    int heuristic_merge(int x, int y){ 
        x = find(x);
        y = find(y);
        if(size[x] < size[y]){
            swap(x, y);
        }
        return merge(x, y);
    }
 
    int get(int x){
        return size[find(x)];
    }
};

vector<vector<int>> get_span(vector<vector<int>> a, int n){
    sort(a.begin(), a.end());
    DSU dsu(n + 1);

    vector<vector<int>> b;
    for(int i = 0; i < a.size(); i++){
        int u = a[i][2], v = a[i][3];
        if(dsu.set(u, v)) continue;
        else{
            dsu.heuristic_merge(u, v);
            b.pb(a[i]); 
        }
    }
    return b;
}

void solve(){
    int n, m;
    cin >> n >> m;

    vector<vector<int>> a, b, vec;
    vector<int> deg(n + 1);

    for(int i = 0; i < m; i++){
        int u, v, w;
        cin >> u >> v >> w;

        if(i < n - 1){
            a.pb({w, 1, u, v, i + 1});
            vec.pb({w, 1, u, v, i + 1});
            deg[u]++;
            deg[v]++;
        }
        else{
            vec.pb({w, 2, u, v, i + 1});
        }
    }

    auto tr = get_span(vec, n);
    map<int, int> mp;

    for(int i = 0; i < a.size(); i++){
        for(int j = 0; j < tr.size(); j++){
            if(a[i][4] == tr[j][4]){
                mp[tr[j][4]] = 1;
            }
        }
    }

    while(1){
        for(int i = 0; i < a.size(); i++){
            if(!mp[a[i][4]]){
                for(int j = 0; j < tr.size(); j++){
                    deg[tr[j][2]]++;
                    deg[tr[j][3]]++;
                    deg[a[i][2]]--;
                    deg[a[i][3]]--;

                    if(mp[tr[j][4]] || !deg[a[i][2]]|| !deg[a[i][3]]){
                        deg[tr[j][2]]--;
                        deg[tr[j][3]]--;
                        deg[a[i][2]]++;
                        deg[a[i][3]]++;
                        continue;
                    }

                    b.pb({a[i][4], tr[j][4]});
                    mp[tr[j][4]] = 1;
                    break;
                }
            }
        }

        int qwq = 0;
        for(int i = 0; i < tr.size(); i++){
            if(mp[tr[i][4]] == 0){
                qwq = 1;
            }
        }
        if(!qwq) break;
    }

    cout << b.size() << endl;
    for(auto p : b){
        cout << p[0] << " " << p[1] << endl;
    }
}

int main(){
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
    cout.tie(nullptr);

    int t = 1;
//    cin >> t;

    while(t--){
        solve();
    }

    return 0;
}