#include <bits/stdc++.h>
using namespace std;
#include <atcoder/all>
using namespace atcoder;
#define rep(i, n) for (ll i = 0; i < (n); ++i)
#define rep1(i, n) for (ll i = 1; i <= n; ++i)
#define reps(i, s, e) for (ll i = s; i <= e; ++i)
#define all(v) v.begin(), v.end()
using ll = long long;
using ld = long double;
using cp = complex<ld>;
using pa = pair<ll, ll>;
using tup = tuple<ll, ll, ll>;
using vp = vector<pair<ll, ll>>;
using vtup = vector<tuple<ll, ll, ll>>;
using st = string;
using vs = vector<string>;
using vc = vector<char>;
using vvi = vector<vector<ll>>;
using vvc = vector<vector<char>>;
using vi = vector<ll>;
const ll MOD1 = 1000000007;
const ll MOD2 = 998244353;
const ll INF = (1LL << 60);

int main() {
  ll n, q;
  cin >> n >> q;
  vector<array<ll, 3>> query(q);
  rep(i, q) {
    ll l, r, b;
    cin >> l >> r >> b;
    l--;
    query[i] = {b, l, r};
  }
  sort(all(query));
  reverse(all(query));

  ll prev = -1;
  vi tmp(n);
  iota(all(tmp), 0);
  set<ll> unused(all(tmp));
  set<ll> used_by_b;

  vi ans(n);
  for (auto [b, l, r] : query) {
    if (b != prev) {
      prev = b;
      used_by_b.clear();
    }

    auto itr = unused.lower_bound(l);
    if (itr == unused.end() || *itr >= r) {
      auto itr2 = used_by_b.lower_bound(l);
      if (itr2 == used_by_b.end() || *itr2 >= r) {
        cout << -1 << endl;
        return 0;
      }
    } else {
      while (itr != unused.end() && *itr < r) {
        ans[*itr] = b;
        used_by_b.insert(*itr);
        itr = unused.erase(itr);
      }
    }
  }

  for (auto i : unused) ans[i] = INF;
  rep(i, n) {
    cout << ans[i];
    if (i == n - 1) {
      cout << endl;
    } else {
      cout << " ";
    }
  }
  return 0;
}