#include <bits/stdc++.h>
#define mp(x, y) make_pair(x, y)
#define fi first 
#define se second
#define ls o << 1
#define rs o << 1 | 1
using namespace std;
typedef long long ll;
#include <chrono>
using namespace chrono;

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

    ll sss = 0;

    vector<pair<pair<ll, pair<ll, ll>>, ll>> e(m + 1);
    vector<bool> mm(m + 1);
    vector<vector<pair<ll, ll>>> g(n + 1);
    for (ll i = 1; i <= m; ++i)
        cin >> e[i].fi.se.fi >> e[i].fi.se.se >> e[i].fi.fi;
    for (ll i = 1; i <= m; ++i) {
        e[i].se = i;
        if (e[i].fi.se.fi > e[i].fi.se.se)
            swap(e[i].fi.se.fi, e[i].fi.se.se);
        if (i <= n - 1)
            sss += e[i].fi.fi, mm[i] = true, g[e[i].fi.se.fi].push_back({e[i].fi.se.se, i}), g[e[i].fi.se.se].push_back({e[i].fi.se.fi, i});
    }
    vector<ll> ee(m + 1);
    vector<ll> del(m + 1);
    vector<pair<ll, ll>> la(n + 1);
    function<bool(ll, ll)> dfs = [&](ll u, ll tt){
        if (u == tt)
            return true;
        for (auto [v, i] : g[u])
            if (v != la[u].fi && !del[i]) {
                la[v] = {u, ee[i]};
                if (dfs(v, tt))
                    return true;
            }
        return false;
    };
    sort(e.begin() + 1, e.end());
    for (ll i = 1; i <= m; ++i)
        ee[e[i].se] = i;
    
    vector<ll> fa(n + 1);
    ll ansss = 0;
    for (ll i = 1; i <= n; ++i)
        fa[i] = i;
    function<ll(ll)> getf = [&](ll o) {
        return o == fa[o] ? o : fa[o] = getf(fa[o]);
    };
    for (ll i = 1; i <= m; ++i)
        if (getf(e[i].fi.se.fi) != getf(e[i].fi.se.se))
            fa[getf(e[i].fi.se.fi)] = getf(e[i].fi.se.se), ansss += e[i].fi.fi;

    vector<pair<ll, ll>> ans;
    for (ll i = 1; i <= m; ++i) {
        ll u = e[i].fi.se.fi, v = e[i].fi.se.se;
        if (mm[e[i].se])
            continue;
        if (sss == ansss)
            break;
        for (int i = 1; i <= n; ++i)
            la[i] = {0, 0};
        dfs(u, v);
        ll pos = -1, mx = e[i].fi.fi, cur = v;
        while (cur != u && cur) {
            if (mx < e[la[cur].se].fi.fi) {
                mx = e[la[cur].se].fi.fi, pos = la[cur].se;
            }
            cur = la[cur].fi;
        }
        // cout << pos << ',' << mx << endl;
        if (pos != -1) {
            g[e[pos].fi.se.fi].erase(find(g[e[pos].fi.se.fi].begin(), g[e[pos].fi.se.fi].end(), make_pair(e[pos].fi.se.se, e[pos].se)));
            g[e[pos].fi.se.se].erase(find(g[e[pos].fi.se.se].begin(), g[e[pos].fi.se.se].end(), make_pair(e[pos].fi.se.fi, e[pos].se)));
            g[u].push_back({v, e[i].se}), g[v].push_back({u, e[i].se});
            mm[e[pos].se] = false;
            mm[e[i].se] = true;
            ans.push_back({e[pos].se, e[i].se});
            sss -= e[pos].fi.fi, sss += e[i].fi.fi;
        }
    }
    cout << ans.size() << '\n';
    for (auto [x, y] : ans)
        cout << x << ' ' << y << '\n';
}

int main() {
auto start = system_clock::now();
    ios_base::sync_with_stdio(false);
    cin.tie(0);
    #ifdef LLOCAL
    freopen("a.in", "r", stdin);
    #endif
    // int t;
    // cin >> t;
    // while (t--)
        solve();

    return 0;
}