fn read() -> (usize, Vec<(usize, usize, u32)>) {
    use std::io::Read;
    let mut s = String::new();
    std::io::stdin().read_to_string(&mut s).unwrap();
    let mut it = s.trim().split_whitespace();
    let mut next = |l: usize, r: usize| -> usize {
        let v = it.next().unwrap().parse::<usize>().unwrap();
        assert!(l <= v && v <= r);
        v
    };
    let n = next(1, 200_000);
    let q = next(1, 200_000);
    let mut cond = vec![(0, 0, 0); q];
    for cond in cond.iter_mut() {
        let l = next(1, n);
        let r = next(l, n);
        let b = next(1, 1_000_000_000) as u32;
        *cond = (l - 1, r, b);
    }
    (n, cond)
}

fn main() {
    let (n, mut cond) = read();
    cond.sort_by_key(|p| p.2);
    let mut set = (0..n).collect::<std::collections::BTreeSet<_>>();
    let inf = 10u32.pow(9);
    let mut ans = vec![inf; n];
    for &(l, r, v) in cond.iter().rev() {
        let x = set.range(l..r).cloned().collect::<Vec<_>>();
        for x in x {
            set.remove(&x);
            ans[x] = v;
        }
    }
    cond.sort_by_key(|p| p.0);
    let mut x = cond.len();
    let mut stack = vec![(inf, n)];
    for (i, &a) in ans.iter().enumerate().rev() {
        while stack.last().map_or(false, |p| p.0 >= a) {
            stack.pop();
        }
        stack.push((a, i));
        while x > 0 && cond[x - 1].0 == i {
            x -= 1;
            let (_, r, v) = cond[x];
            if stack
                .binary_search_by_key(&v, |p| p.0)
                .map_or(true, |p| stack[p].1 >= r)
            {
                println!("-1");
                return;
            }
        }
    }
    let s = ans
        .iter()
        .map(|a| a.to_string())
        .collect::<Vec<_>>()
        .join(" ");
    println!("{}", s);
}