#define MOD_TYPE 2

#pragma region Macros
#include <bits/stdc++.h>
using namespace std;
/*
#include <boost/multiprecision/cpp_int.hpp>
#include <boost/multiprecision/cpp_dec_float.hpp>
using multiInt = boost::multiprecision::cpp_int;
using lld = boost::multiprecision::cpp_dec_float_100;
*/

#pragma GCC target("avx2")
#pragma GCC optimize("O3")
#pragma GCC optimize("unroll-loops")

using ll = long long int;
using ld = long double;
using pii = pair<int, int>;
using pll = pair<ll, ll>;
using pld = pair<ld, ld>;
template <typename Q_type>
using smaller_queue = priority_queue<Q_type, vector<Q_type>, greater<Q_type>>;

constexpr ll MOD = (MOD_TYPE == 1 ? (ll)(1e9 + 7) : 998244353);
constexpr int INF = (int)1e9;
constexpr ll LINF = (ll)4e18;
constexpr ld PI = acos(-1.0);
constexpr ld EPS = 1e-11;
constexpr int Dx[] = {0, 0, -1, 1, -1, 1, -1, 1, 0};
constexpr int Dy[] = {1, -1, 0, 0, -1, -1, 1, 1, 0};

#define REP(i, m, n) for (ll i = m; i < (ll)(n); ++i)
#define rep(i, n) REP(i, 0, n)
#define REPI(i, m, n) for (int i = m; i < (int)(n); ++i)
#define repi(i, n) REPI(i, 0, n)
#define MP make_pair
#define MT make_tuple
#define YES(n) cout << ((n) ? "YES" : "NO") << "\n"
#define Yes(n) cout << ((n) ? "Yes" : "No") << "\n"
#define possible(n) cout << ((n) ? "possible" : "impossible") << "\n"
#define Possible(n) cout << ((n) ? "Possible" : "Impossible") << "\n"
#define Yay(n) cout << ((n) ? "Yay!" : ":(") << "\n"
#define all(v) v.begin(), v.end()
#define NP(v) next_permutation(all(v))
#define dbg(x) cerr << #x << ":" << x << "\n";

inline void init_main()
{
  cin.tie(0);
  ios::sync_with_stdio(false);
  cout << setprecision(30) << setiosflags(ios::fixed);
}
template <typename T>
inline bool chmin(T &a, T b)
{
  if (a > b)
  {
    a = b;
    return true;
  }
  return false;
}
template <typename T>
inline bool chmax(T &a, T b)
{
  if (a < b)
  {
    a = b;
    return true;
  }
  return false;
}
inline ll CEIL(ll a, ll b)
{
  return (a + b - 1) / b;
}
template <typename A, size_t N, typename T>
inline void Fill(A (&array)[N], const T &val)
{
  fill((T *)array, (T *)(array + N), val);
}
#pragma endregion

int main()
{
  init_main();

  int n, q;
  cin >> n >> q;
  vector<tuple<int, int, int>> query(q);
  rep(i, q)
  {
    int a, b, c;
    cin >> a >> b >> c;
    a--, b--;
    query[i] = MT(c, a, b);
  }
  sort(all(query), greater<tuple<int, int, int>>());

  int before = -1;
  vector<int> temp(n);
  iota(all(temp), 0);
  set<int> unused(all(temp)), 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] = INF;
  rep(i, n) cout << ans[i] << (i+1==n ? '\n' : ' ');
  return 0;
}