#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);

using S = int;
using F = int;
S op(S a, S b) { return min(a, b); }
S e() { return int(1e9); }
S mapping(F x, S a) { return x == -1 ? a : x; }
F composition(F f, F g) { return f == -1 ? g : f; }
F id() { return -1; }

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));
  lazy_segtree<S, op, e, F, mapping, composition, id> seg(n);

  for (auto [b, l, r] : query) {
    seg.apply(l, r, b);
  }

  for (auto [b, l, r] : query) {
    if (seg.prod(l, r) != b) {
      cout << -1 << endl;
      return 0;
    }
  }

  rep(i, n) {
    cout << seg.get(i);
    if (i != n - 1) {
      cout << " ";
    } else {
      cout << endl;
    }
  }

  return 0;
}