#include <bits/stdc++.h>

#include <atcoder/all>
using namespace std;
using ll = long long;
#define rep(i, n) for (int i = 0; i < int(n); i++)
#define all(v) v.begin(), v.end()

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() {
  int n, q;
  cin >> n >> q;
  vector<array<int, 3>> query(q);
  rep(i, q) {
    int l, r, b;
    cin >> l >> r >> b;
    l--;
    query[i] = {b, l, r};
  }
  sort(all(query));
  atcoder::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 << "\n";
      return 0;
    }
  }
  rep(i, n) cout << seg.get(i) << (i + 1 == n ? "\n" : " ");
}