#include <bits/stdc++.h>
using namespace std;
int read() {
  char c;
  int x;
  while (c = getchar(), c < '0' || c > '9')
    ;
  x = c - '0';
  while (c = getchar(), c >= '0' && c <= '9') x = x * 10 + c - '0';
  return x;
}
int n, m, k, tot, fa[5005], vis[100005], l, r, mid, ans;
struct node {
  int a, b, len, id;
} F[100005];
int cmp(node a, node b) {
  if (a.len < b.len)
    return 1;
  else if (a.len == b.len) {
    if (a.a == 1 || a.b == 1) return 1;
  }
  return 0;
}
int find(int x) {
  if (fa[x] != x) fa[x] = find(fa[x]);
  return fa[x];
}
void unionn(int x, int y) {
  x = find(x);
  y = find(y);
  fa[y] = x;
}
int check(int x) {
  for (int i = 1; i <= n; i++) fa[i] = i;
  for (int i = 1; i <= m; i++) {
    if (F[i].a == 1 || F[i].b == 1) F[i].len += x;
  }
  sort(F + 1, F + 1 + m, cmp);
  int p = 0, res = 0;
  for (int i = 1; i <= m; i++) {
    if (p == n - 1) break;
    if ((F[i].a == 1 || F[i].b == 1) && res == k) continue;
    if (find(F[i].a) != find(F[i].b)) {
      unionn(F[i].a, F[i].b);
      p++;
      if (F[i].a == 1 || F[i].b == 1) res++;
    }
  }
  for (int i = 1; i <= m; i++) {
    if (F[i].a == 1 || F[i].b == 1) F[i].len -= x;
  }
  return res >= k;
}
int main() {
  n = read();
  m = read();
  k = read();
  for (int i = 1; i <= m; i++) {
    F[i].a = read();
    F[i].b = read();
    F[i].len = read();
    F[i].id = i;
  }
  l = -100000, r = 100000;
  while (l <= r) {
    mid = (l + r) >> 1;
    if (check(mid))
      l = mid + 1, ans = mid;
    else
      r = mid - 1;
  }
  for (int i = 1; i <= m; i++) {
    if (F[i].a == 1 || F[i].b == 1) F[i].len += ans;
  }
  sort(F + 1, F + 1 + m, cmp);
  int p = 0, res = 0;
  for (int i = 1; i <= n; i++) fa[i] = i;
  for (int i = 1; i <= m; i++) {
    if (p == n - 1) break;
    if ((F[i].a == 1 || F[i].b == 1) && res == k) continue;
    if (find(F[i].a) != find(F[i].b)) {
      unionn(F[i].a, F[i].b);
      p++;
      vis[F[i].id] = 1;
      if (F[i].a == 1 || F[i].b == 1) res++;
    }
  }
  if (p < n - 1 || res != k) {
    puts("-1");
  } else {
    printf("%d\n", n - 1);
    for (int i = 1; i <= m; i++)
      if (vis[i]) printf("%d ", i);
  }
  return 0;
}
