#include <bits/stdc++.h>
#include <atcoder/modint>
using namespace std;
using namespace atcoder;
using mint = modint998244353;
//using mint = modint1000000007;
using ll = long long;
using ld = long double;
using pll = pair<ll, ll>;
using tlll = tuple<ll, ll, ll>;
constexpr ll INF = 1LL << 60;
template<class T> bool chmin(T& a, T b) {if (a > b) {a = b; return true;} return false;}
template<class T> bool chmax(T& a, T b) {if (a < b) {a = b; return true;} return false;}
ll safemod(ll A, ll M) {return (A % M + M) % M;}
ll divfloor(ll A, ll B) {if (B < 0) {return divfloor(-A, -B);} return (A - safemod(A, B)) / B;}
ll divceil(ll A, ll B) {if (B < 0) {return divceil(-A, -B);} return divfloor(A + B - 1, B);}
#define FINALANS(A) do {cout << (A) << '\n'; exit(0);} while (false)

#include <atcoder/lazysegtree>

ll op(ll a, ll b)
{
  return min(a, b);
}

ll e()
{
  return INF;
}

ll mapping(ll f, ll x)
{
  return (f == INF ? x : f);
}

ll composition(ll f, ll g)
{
  return (f == INF ? g : f);
}

ll id()
{
  return INF;
}

int main()
{
  ll N, Q;
  cin >> N >> Q;
  vector<tlll> BLR(Q);
  for (ll q = 0; q < Q; q++)
  {
    ll l, r, b;
    cin >> l >> r >> b;
    l--;
    BLR.at(q) = make_tuple(b, l, r);
  }

  sort(BLR.begin(), BLR.end());

  lazy_segtree<ll, op, e, ll, mapping, composition, id> seg(N);
  for (ll q = 0; q < Q; q++)
  {
    auto blr = BLR.at(q);
    ll b = get<0>(blr), l = get<1>(blr), r = get<2>(blr);

    seg.apply(l, r, b);
  }

  for (ll i = 0; i < N; i++)
  {
    if (seg.get(i) == INF)
      seg.set(i, 1e9);
  }

  for (ll q = 0; q < Q; q++)
  {
    auto blr = BLR.at(q);
    ll b = get<0>(blr), l = get<1>(blr), r = get<2>(blr);

    if (seg.prod(l, r) != b)
      FINALANS(-1);
  }

  for (ll i = 0; i < N; i++)
  {
    cout << seg.get(i) << (i == N - 1 ? '\n' : ' ');
  }
}