#include "bits/stdc++.h"

using lint = int64_t;

using namespace std;

int main() {
    cin.tie(nullptr)->sync_with_stdio(false);
    int n, m;
    cin>>n>>m;
    vector<array<int, 4>>edges(m);
    for(int i=0;i<m;i++){
        int a, b, c;
        cin>>a>>b>>c;
        a--, b--;
        edges[i] = {c, a, b, i};
    }
    vector<int>p(n), cnt(n);
    for(int i=0;i<n;i++) p[i] = i, cnt[i] = 1;
    auto find = [&](auto& self, int u)->int {
        if(p[u] == u) return u;
        return p[u] = self(self, p[u]);
    };
    auto same_comp = [&](int u, int v)->bool {
        u = find(find, u), v = find(find, v);
        return u == v;
    };
    auto join = [&](int u, int v)->void {
        u = find(find, u), v = find(find, v);
        if(u == v) return;
        if(cnt[u] < cnt[v]) swap(u, v);
        p[v] = u;
        cnt[u] += cnt[v];
    };

    sort(edges.begin(), edges.end());
    vector<pair<int, int>>ans;

    for(int i=0;i<m;i++){
        auto [c, a, b, id] = edges[i];
        if(same_comp(a, b)) continue;
        if(id < n - 1){
            join(a, b);
            continue;
        }
        auto cp = p, ccnt = cnt;
        for(int j=i+1;j<m;j++){
            auto [f, d, e, id2] = edges[j];
            if(id2 < n - 1){
                join(d, e);
                if(same_comp(a, b)){
                    if(f > c) ans.push_back({id, id2});
                    break;
                }
            }
        }
        swap(p, cp);
        swap(cnt, ccnt);
    }
    cout<<size(ans)<<"\n";
    for(auto [u, v] : ans) cout<<v+1<<" "<<u+1<<"\n";


    return 0;
}