#include <bits/stdc++.h>
using namespace std;
const int MAX_N = 5000 + 10;
vector<pair<pair<long double, int>, pair<int, int>>> ed, ed1;
vector<int> vec;
int par[MAX_N];
int get_par(int u) { return ~par[u] ? (par[u] = get_par(par[u])) : u; }
bool merge(int u, int v) {
  u = get_par(u), v = get_par(v);
  if (u == v) return false;
  par[u] = v;
  return true;
}
int check(long double x) {
  ed1 = ed;
  for (int i = 0; i < ((int)(ed1).size()); i++)
    ed1[i].first.first += (ed1[i].second.first == 0) * x;
  int cnt = 0;
  vec.clear();
  memset(par, -1, sizeof par);
  sort(ed1.begin(), ed1.end());
  for (int i = 0; i < ((int)(ed1).size()); i++) {
    int u = ed1[i].second.first, v = ed1[i].second.second;
    if (merge(u, v)) vec.push_back(ed1[i].first.second), cnt += (u == 0);
  }
  return cnt;
}
int main() {
  ios_base ::sync_with_stdio(false), cin.tie(NULL), cout.tie(NULL);
  int n, m, k;
  cin >> n >> m >> k;
  for (int i = 0; i < m; i++) {
    int u, v, w;
    cin >> u >> v >> w;
    u--, v--;
    if (u > v) swap(u, v);
    ed.push_back(make_pair(make_pair(w, i), make_pair(u, v)));
  }
  long double L = -1e6, R = 1e6;
  for (int i = 0; i < 200; i++) {
    long double mid = (L + R) / 2;
    check(mid) < k ? R = mid : L = mid;
  }
  if (check(L) != k) return cout << "-1\n", 0;
  cout << n - 1 << endl;
  for (auto i : vec) cout << i + 1 << ' ';
  return 0;
}
