#include <bits/stdc++.h>
using namespace std;
int n, m, k;
vector<pair<long long, pair<int, int> > > o, v;
int pai[100100];
map<pair<int, int>, int> ma;
vector<int> ans;
void init(int n) {
  for (int i = 1; i <= n; i++) {
    pai[i] = i;
  }
}
int find(int i) {
  if (pai[i] == i) return i;
  return pai[i] = find(pai[i]);
}
void join(int a, int b) {
  a = find(a);
  b = find(b);
  pai[a] = pai[b];
}
int tree(long long x) {
  v = o;
  for (int i = 0; i < m; i++) {
    if (v[i].second.first == 1 or v[i].second.second == 1) v[i].first += x + i;
  }
  init(n);
  ans.clear();
  sort(v.begin(), v.end());
  int d = 0;
  for (auto p : v) {
    int a = p.second.first, b = p.second.second;
    if (find(a) == find(b)) continue;
    join(a, b);
    ans.push_back(ma[p.second]);
    if (a == 1 or b == 1) d++;
  }
  return d;
}
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  cin >> n >> m >> k;
  for (int i = 0; i < m; i++) {
    long long a, b, c;
    cin >> a >> b >> c;
    c *= 1000000;
    o.push_back({c, {a, b}});
    ma[{a, b}] = i + 1;
  }
  sort(o.begin(), o.end());
  long long l = -1e12, r = 1e12;
  while (l < r) {
    long long mid = floor((l + r) / 2.0);
    int t = tree(mid);
    if (t < k) {
      r = mid;
    }
    if (t > k) {
      l = mid + 1;
    }
    if (t == k) {
      cout << ans.size() << endl;
      for (auto i : ans) cout << i << " ";
      return 0;
    }
  }
  cout << -1;
}
