using static System.Math;
using System.Linq;
using System;

public class P
{
    public int L { get; set; }
    public int r { get; set; }
    public int b { get; set; }
}

public class Hello
{
    public static int BIG = 1000000000;
    static void Main()
    {
        string[] line = Console.ReadLine().Trim().Split(' ');
        var n = int.Parse(line[0]);
        var q = int.Parse(line[1]);
        var ps = new P[q];
        for (int i = 0; i < q; i++)
        {
            line = Console.ReadLine().Trim().Split(' ');
            var L = int.Parse(line[0]) - 1;
            var r = int.Parse(line[1]) - 1;
            var b = int.Parse(line[2]);
            ps[i] = new P { L = L, r = r, b = b };
        }
        getAns(n, q, ps);
    }
    static void getAns(int n, int q, P[] ps)
    {
        var ans = Enumerable.Repeat(BIG, n).ToArray();
        var d = n;
        var pre = BIG;
        foreach (var x in ps.OrderByDescending(x => x.b).ThenByDescending(x => x.L))
        {
            var ok = false;
            var imin = Min(d - 1, x.r);
            for (int i = imin; i >= x.L; i--)
            {
                if (ans[i] > x.b) { ans[i] = x.b; ok = true;}
            }
            if (!ok && pre != x.b) { Console.WriteLine(-1); return; }
            d = x.L;
            pre = x.b;
        }
        Console.WriteLine(string.Join(" ", ans));
    }
}