#include <bits/stdc++.h>
using namespace std;
const long long MaxN = 5E3 + 10;
const long long MaxM = 1E5 + 10;
const long long MaxW = 1E5 + 10;
const long double eps = 1E-8;
const long long INF = 1E9 + 7;
const long long MOD = 1000 * 1000 * 1000 + 7;
long long n, m, k;
long long h[MaxN], deg[MaxN], par[MaxN];
vector<long long> ans;
long long pow(long long n, long long k) {
  if (k == 0) return 1;
  long long cnt = pow(n, k / 2);
  if (k % 2 == 0)
    return (cnt * cnt) % MOD;
  else
    return (n * pow(n, k - 1)) % MOD;
}
struct edge {
  long long u;
  long long v;
  long long w;
  long long ind;
} e[MaxM];
bool cmp(edge a, edge b) {
  if (a.w == b.w) {
    if (a.u == 0 || a.v == 0) return true;
    return false;
  }
  return a.w < b.w;
}
long long find_root(long long v) {
  if (par[v] == v) return v;
  return par[v] = find_root(par[v]);
}
void addEdge(long long m) {
  long long u = e[m].u;
  long long v = e[m].v;
  if (u > v) swap(u, v);
  if (u == 0 && deg[u] == k) return;
  long long ru = find_root(u);
  long long rv = find_root(v);
  if (h[ru] < h[rv])
    par[ru] = rv;
  else if (h[ru] > h[rv])
    par[rv] = ru;
  else {
    par[ru] = rv;
    ++h[rv];
  }
  ++deg[u];
  ++deg[v];
  ans.push_back(e[m].ind);
}
bool MST(long long val) {
  ans.clear();
  for (long long i = 0; i < n; ++i) {
    par[i] = i;
    h[i] = 0;
    deg[i] = 0;
  }
  for (long long i = 0; i < m; ++i)
    if (e[i].u == 0 || e[i].v == 0) e[i].w -= val;
  sort(e, e + m, cmp);
  for (long long i = 0; i < m; ++i)
    if (find_root(e[i].u) != find_root(e[i].v)) addEdge(i);
  for (long long i = 0; i < m; ++i)
    if (e[i].u == 0 || e[i].v == 0) e[i].w += val;
  for (long long i = 0; i < n; ++i)
    if (deg[i] == 0) return false;
  return (deg[0] == k);
}
int32_t main() {
  ios::sync_with_stdio(false);
  cin.tie();
  cout.tie();
  cout << fixed << setprecision(12);
  cin >> n >> m >> k;
  for (long long i = 0; i < m; ++i) {
    cin >> e[i].u >> e[i].v >> e[i].w;
    --e[i].u;
    --e[i].v;
    e[i].ind = i + 1;
  }
  if (n == 1 && k == 0) {
    cout << 0;
    return 0;
  }
  if (!MST(MaxW)) {
    cout << -1;
    return 0;
  }
  long long l = -MaxW, r = MaxW;
  while (r - l > 1) {
    long long mid = (l + r) / 2;
    if (MST(mid))
      r = mid;
    else
      l = mid;
  }
  MST(r);
  cout << ans.size() << endl;
  for (long long i = 0; i < ans.size(); ++i) cout << ans[i] << " ";
}
