#include <cassert>
#include <cmath>
#include <algorithm>
#include <iostream>
#include <iomanip>
#include <climits>
#include <map>
#include <queue>
#include <set>
#include <cstring>
#include <vector>

using namespace std;
typedef long long ll;

struct Command {
  int type;
  int num;

  Command(int type = -1, int num = -1) {
    this->type = type;
    this->num = num;
  }
};

const double R = 1e-10;

struct Node {
  int i;
  int v;

  Node(int i = -1, int v = -1) {
    this->i = i;
    this->v = v;
  }

  bool operator>(const Node &n) const {
    return v - i * R < n.v - n.i * R;
  }
};

struct Query {
  int l;
  int r;
  int B;

  Query(int l = -1, int r = -1, int B = -1) {
    this->l = l;
    this->r = r;
    this->B = B;
  }

  bool operator>(const Query &n) const {
    return B - l * R < n.B - n.l * R;
  }
};

int main() {
  int N, Q;
  cin >> N >> Q;

  vector<Command> commands[N + 2];
  priority_queue <Query, vector<Query>, greater<Query>> p_query;
  for (int i = 0; i < Q; ++i) {
    int l, r, B;
    cin >> l >> r >> B;

    commands[l].push_back(Command(0, B));
    commands[r + 1].push_back(Command(1, B));
    p_query.push(Query(l, r, B));
  }

  map<int, int> counter;
  priority_queue <int> pque;
  pque.push(1);
  counter[1]++;
  int ans[N + 1];

  for (int i = 1; i <= N; ++i) {
    for (Command &cmd : commands[i]) {
      if (cmd.type == 0) {
        pque.push(cmd.num);
        counter[cmd.num]++;
      } else {
        counter[cmd.num]--;
      }
    }

    while (not pque.empty() && counter[pque.top()] == 0) {
      pque.pop();
    }

    ans[i] = pque.top();
  }

  priority_queue <Node, vector<Node>, greater<Node>> pque2;
  for (int i = 1; i <= N; ++i) {
    pque2.push(Node(i, ans[i]));
  }

  while (not pque2.empty()) {
    Node node = pque2.top();
    pque2.pop();

    while (not p_query.empty()) {
      Query q = p_query.top();
      if (q.B != node.v) break;

      if (q.l <= node.i && node.i <= q.r) {
        p_query.pop();
      } else {
        break;
      }
    }
  }

  if (p_query.empty()) {
    for (int i = 1; i <= N; ++i) {
      cout << ans[i];
      if (i < N) cout << " ";
    }
    cout << endl;
  } else {
    cout << -1 << endl;
  }

  return 0;
}