import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.util.Arrays;
import java.util.PriorityQueue;
import java.util.Set;
import java.util.TreeSet;

public class Main {
	public static void main(String[] args) throws Exception {
		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
		String[] sa = br.readLine().split(" ");
		int n = Integer.parseInt(sa[0]);
		int q = Integer.parseInt(sa[1]);
		PriorityQueue<Obj> que = new PriorityQueue<>((o1, o2) -> o2.b - o1.b);
		for (int i = 0; i < q; i++) {
			sa = br.readLine().split(" ");
			Obj o = new Obj();
			o.l = Integer.parseInt(sa[0]) - 1;
			o.r = Integer.parseInt(sa[1]);
			o.b = Integer.parseInt(sa[2]);
			que.add(o);
		}
		br.close();

		int[] a = new int[n];
		Arrays.fill(a, 1);
		TreeSet<Integer> set = new TreeSet<>();
		for (int i = 0; i < n; i++) {
			set.add(i);
		}
		Obj pre = null;
		while (!que.isEmpty()) {
			Obj o = que.poll();
			Set<Integer> ss = set.subSet(o.l, o.r);
			if (pre != null && o.b < pre.b && ss.isEmpty()) {
				System.out.println(-1);
				return;
			}
			for (int i : ss) {
				a[i] = o.b;
			}
			ss.clear();
			pre = o;
		}
		StringBuilder sb = new StringBuilder();
		for (int i = 0; i < n; i++) {
			sb.append(a[i]).append(' ');
		}
		sb.deleteCharAt(sb.length() - 1);
		System.out.println(sb.toString());
	}

	static class Obj {
		int l, r, b;
	}
}