#include <bits/stdc++.h>
using namespace std;
#define all(v) v.begin(), v.end()

int main()
{
  int n, q;
  cin >> n >> q;
  vector<array<int, 3>> query(q);
  for (int i = 0; i < q; i++)
  {
    int a, b, c;
    cin >> a >> b >> c;
    a--, b--;
    query[i] = {c, a, b};
  }
  sort(all(query));
  reverse(all(query));

  int before = -1;
  vector<int> tmp(n);
  iota(all(tmp), 0);
  set<int> unused(all(tmp)), used_i;

  vector<int> ans(n);
  for (auto [b, l, r] : query)
  {
    if (b != before)
    {
      before = b;
      used_i.clear();
    }
    auto itr = unused.lower_bound(l);
    if (itr == unused.end() || *itr > r) // 更新可能なものがない
    {
      auto itr_i = used_i.lower_bound(l);
      if (itr_i == used_i.end() || *itr_i > r)
      {
        cout << -1 << endl;
        return 0;
      }
    }
    else // 更新可能なものがある
    {
      while (itr != unused.end() && *itr <= r)
      {
        ans[*itr] = b;
        used_i.insert(*itr);
        itr = unused.erase(itr);
      }
    }
  }

  for (auto i : unused)
    ans[i] = int(1e9);
  for (int i = 0; i < n; i++)
    cout << ans[i] << (i + 1 == n ? "" : " ");
  return 0;
}