#include <bits/stdc++.h>
using namespace std;

#define rep(i, a, b) for (int i = (a); i < (b); i++)
#define all(x) begin(x), end(x)
#define sz(x) int((x).size())
using ll = long long;
using pii = pair<int, int>;
using vi = vector<int>;

#ifdef LOCAL
auto operator<<(auto& o, auto x) -> decltype(x.first, o);
auto operator<<(auto& o, auto x) -> decltype(x.end(), o) {
  o << "{";
  for (int i = 0; auto y : x) o << ", " + !i++ * 2 << y;
  return o << "}";
}
auto operator<<(auto& o, auto x) -> decltype(x.first, o) {
  return o << "(" << x.first << ", " << x.second << ")";
}
void __print(auto... x) { ((cerr << x << " "), ...) << endl; }
#define debug(x...) __print("[" #x "]:", x)
#else
#define debug(...) 2137
#endif

vector<vector<pair<int, int>>> g;
vector<int> tr, res;

vector<int> c1, c2;

vector<int> p, rnk;
int repr(int a) {
  if(a == p[a]) return a;
  return p[a] = repr(p[a]);
}

bool un(int a, int b) {
  a = repr(a);
  b = repr(b);
  if(a == b) return false;
  if(rnk[a] < rnk[b]) swap(a, b);
  p[b] = a;
  if(rnk[a] == rnk[b]) rnk[a]++;
  return true;
}

void dfs(int v, int col, int par = -1) {
  if(col == 1) c1[v] = 1;
  else c2[v] = 1;
  for(auto [to, id] : g[v]) {
    if(to == par || !tr[id]) continue;
    dfs(to, col, v);
  }
}

int main() {
  cin.tie(0)->sync_with_stdio(0);
  int n, m;
  cin >> n >> m;
  g.resize(n);

  p.resize(n);
  iota(p.begin(), p.end(), 0);
  rnk.assign(n, 1);

  vector<ll> a(m + 1), b(m + 1), w(m + 1);
  tr.resize(m + 1);
  res.resize(m + 1);
  vector<pair<ll, int>> e;
  for(int i = 1; i <= m; i++) {
    cin >> a[i] >> b[i] >> w[i];
    a[i]--;
    b[i]--;
    if(i <= n - 1) tr[i] = 1;
    e.push_back({w[i], i});
    g[a[i]].push_back({b[i], i});
    g[b[i]].push_back({a[i], i});
  }
  sort(e.begin(), e.end());
  for(int i = 0; i < m; i++) {
    int x = a[e[i].second];
    int y = b[e[i].second];
    if(un(x, y)) {
      res[e[i].second] = 1;
    }
  }

  debug(g);
  debug(a);
  debug(b);
  debug(w);
  debug(tr);
  debug(res);

  vector<pair<int, int>> ans;
  while(true) {
    int ind = -1;
    int x, y;
    for(int i = 1; i <= m; i++) {
      if(tr[i] && !res[i]) {
        ind = i;
        x = a[ind];
        y = b[ind];
      }
    }
    if(ind == -1) break;
    c1.assign(n, 0);
    c2.assign(n, 0);
    tr[ind] = 0;

    debug(tr, ind);
    
    dfs(x, 1);
    dfs(y, 2);

    int add = -1;
    for(int i = 1; i <= m; i++) {
      if(c1[a[i]] && c2[b[i]] || c1[b[i]] && c2[a[i]]) {
        if(res[i]) add = i;
      }
    }

    tr[add] = 1;
    ans.push_back({ind, add}); 
  }

  cout << ans.size() << '\n';
  for(int i = 0; i < ans.size(); i++) {
    cout << ans[i].first << " " << ans[i].second << '\n';
  }
}