#include <bits/stdc++.h>
using namespace std;
const int N = 5005, M = 100005;
int re() {
  int x = 0, w = 1;
  char ch = getchar();
  while (ch < '0' || ch > '9') {
    if (ch == '-') w = -1;
    ch = getchar();
  }
  while (ch >= '0' && ch <= '9') x = x * 10 + ch - '0', ch = getchar();
  return x * w;
}
int n, m, k, num, s, fa[N], tmp[M];
struct edge {
  int u, v, w, id;
} E[M];
bool cmp(edge x, edge y) { return x.w == y.w ? x.u < y.u : x.w < y.w; }
int find(int x) { return x == fa[x] ? x : fa[x] = find(fa[x]); }
void check(int mid, int o) {
  for (int i = 1; i <= m; i++)
    if (E[i].u == 1) E[i].w += mid;
  sort(E + 1, E + m + 1, cmp);
  num = s = 0;
  for (int i = 1; i <= n; i++) fa[i] = i;
  for (int i = 1; i <= m; i++) {
    int x = E[i].u, y = E[i].v;
    if (o && s == k && x == 1) continue;
    if (find(x) ^ find(y)) {
      fa[fa[x]] = fa[y], tmp[++num] = E[i].id;
      if (x == 1) s++;
    }
    if (num == n - 1) break;
  }
  for (int i = 1; i <= m; i++)
    if (E[i].u == 1) E[i].w -= mid;
}
int main() {
  n = re(), m = re(), k = re();
  for (int i = 1, u, v, w; i <= m; i++) {
    u = re(), v = re(), w = re();
    if (u > v) swap(u, v);
    E[i] = (edge){u, v, w, i};
  }
  int l = -100000, r = 100000, ans = l;
  while (l <= r) {
    int mid = (l + r) >> 1;
    check(mid, 0);
    if (s < k)
      r = mid - 1;
    else
      l = mid + 1, ans = mid;
  }
  check(ans, 1);
  if (num != n - 1 || s < k) {
    puts("-1");
    return 0;
  }
  printf("%d\n", n - 1);
  for (int i = 1; i < n; i++) printf("%d ", tmp[i]);
  return 0;
}
