#[allow(unused_imports)]
use std::cmp::*;
#[allow(unused_imports)]
use std::collections::*;
use std::io::{Write, BufWriter};
// https://qiita.com/tanakh/items/0ba42c7ca36cd29d0ac8
macro_rules! input {
    ($($r:tt)*) => {
        let stdin = std::io::stdin();
        let mut bytes = std::io::Read::bytes(std::io::BufReader::new(stdin.lock()));
        let mut next = move || -> String{
            bytes.by_ref().map(|r|r.unwrap() as char)
                .skip_while(|c|c.is_whitespace())
                .take_while(|c|!c.is_whitespace())
                .collect()
        };
        input_inner!{next, $($r)*}
    };
}

macro_rules! input_inner {
    ($next:expr) => {};
    ($next:expr,) => {};
    ($next:expr, $var:ident : $t:tt $($r:tt)*) => {
        let $var = read_value!($next, $t);
        input_inner!{$next $($r)*}
    };
}

macro_rules! read_value {
    ($next:expr, ( $($t:tt),* )) => { ($(read_value!($next, $t)),*) };
    ($next:expr, [ $t:tt ; $len:expr ]) => {
        (0..$len).map(|_| read_value!($next, $t)).collect::<Vec<_>>()
    };
    ($next:expr, chars) => {
        read_value!($next, String).chars().collect::<Vec<char>>()
    };
    ($next:expr, usize1) => (read_value!($next, usize) - 1);
    ($next:expr, [ $t:tt ]) => {{
        let len = read_value!($next, usize);
        read_value!($next, [$t; len])
    }};
    ($next:expr, $t:ty) => ($next().parse::<$t>().expect("Parse error"));
}

// Verified by: https://atcoder.jp/contests/joisc2021/submissions/25693167
pub trait Action {
    type T: Clone + Copy; // data
    type U: Clone + Copy + PartialEq + Eq; // action
    fn update(x: Self::T, a: Self::U) -> Self::T;
    fn upop(fst: Self::U, snd: Self::U) -> Self::U;
    fn upe() -> Self::U; // identity for upop
}
pub struct DualSegTree<R: Action> {
    n: usize,
    dat: Vec<R::T>,
    lazy: Vec<R::U>,
}

impl<R: Action> DualSegTree<R> {
    pub fn new(a: &[R::T]) -> Self {
        let n_ = a.len();
        let mut n = 1;
        while n < n_ { n *= 2; } // n is a power of 2
        DualSegTree {
            n: n,
            dat: a.to_vec(),
            lazy: vec![R::upe(); 2 * n - 1]
        }
    }
    #[inline]
    fn lazy_evaluate_node(&mut self, k: usize) {
        if self.lazy[k] == R::upe() { return; }
        if k >= self.n - 1 {
            let idx = k + 1 - self.n;
            self.dat[idx] = R::update(self.dat[idx], self.lazy[k]);
        }
        if k < self.n - 1 {
            self.lazy[2 * k + 1] = R::upop(self.lazy[2 * k + 1], self.lazy[k]);
            self.lazy[2 * k + 2] = R::upop(self.lazy[2 * k + 2], self.lazy[k]);
        }
        self.lazy[k] = R::upe(); // identity for upop
    }
    fn update_sub(&mut self, a: usize, b: usize, v: R::U, k: usize, l: usize, r: usize) {
        self.lazy_evaluate_node(k);

        // [a,b) and  [l,r) intersects?
        if r <= a || b <= l {return;}
        if a <= l && r <= b {
            self.lazy[k] = R::upop(self.lazy[k], v);
            self.lazy_evaluate_node(k);
            return;
        }

        self.update_sub(a, b, v, 2 * k + 1, l, (l + r) / 2);
        self.update_sub(a, b, v, 2 * k + 2, (l + r) / 2, r);
    }
    /* ary[i] = upop(ary[i], v) for i in [a, b) (half-inclusive) */
    #[inline]
    pub fn update(&mut self, a: usize, b: usize, v: R::U) {
        let n = self.n;
        self.update_sub(a, b, v, 0, 0, n);
    }
    /* l,r are for simplicity */
    fn update_at_sub(&mut self, a: usize, k: usize, l: usize, r: usize) {
        self.lazy_evaluate_node(k);

        // [a,a+1) and  [l,r) intersect?
        if r <= a || a + 1 <= l { return; }
        if a <= l && r <= a + 1 { return; }
        self.update_at_sub(a, 2 * k + 1, l, (l + r) / 2);
        self.update_at_sub(a, 2 * k + 2, (l + r) / 2, r);
    }
    /* [a, b) (note: half-inclusive) */
    #[inline]
    pub fn query(&mut self, a: usize) -> R::T {
        let n = self.n;
        self.update_at_sub(a, 0, 0, n);
        self.dat[a]
    }
}

enum Chmax {}

impl Action for Chmax {
    type T = i64; // data
    type U = i64; // action, a |-> x |-> max(x, a)
    fn update(x: Self::T, a: Self::U) -> Self::T {
        max(x, a)
    }
    fn upop(fst: Self::U, snd: Self::U) -> Self::U {
        std::cmp::max(fst, snd)
    }
    fn upe() -> Self::U { // identity for upop
        -1 << 50
    }
}

/**
 * Segment Tree. This data structure is useful for fast folding on intervals of an array
 * whose elements are elements of monoid I. Note that constructing this tree requires the identity
 * element of I and the operation of I.
 * Verified by: yukicoder No. 259 (http://yukicoder.me/submissions/100581)
 *              AGC015-E (http://agc015.contest.atcoder.jp/submissions/1461001)
 */
struct SegTree<I, BiOp> {
    n: usize,
    dat: Vec<I>,
    op: BiOp,
    e: I,
}

impl<I, BiOp> SegTree<I, BiOp>
    where BiOp: Fn(I, I) -> I,
          I: Copy {
    pub fn new(n_: usize, op: BiOp, e: I) -> Self {
        let mut n = 1;
        while n < n_ { n *= 2; } // n is a power of 2
        SegTree {n: n, dat: vec![e; 2 * n - 1], op: op, e: e}
    }
    /* ary[k] <- v */
    pub fn update(&mut self, idx: usize, v: I) {
        let mut k = idx + self.n - 1;
        self.dat[k] = v;
        while k > 0 {
            k = (k - 1) / 2;
            self.dat[k] = (self.op)(self.dat[2 * k + 1], self.dat[2 * k + 2]);
        }
    }
    /* [a, b) (note: half-inclusive)
     * http://proc-cpuinfo.fixstars.com/2017/07/optimize-segment-tree/ */
    pub fn query(&self, mut a: usize, mut b: usize) -> I {
        let mut left = self.e;
        let mut right = self.e;
        a += self.n - 1;
        b += self.n - 1;
        while a < b {
            if (a & 1) == 0 {
                left = (self.op)(left, self.dat[a]);
            }
            if (b & 1) == 0 {
                right = (self.op)(self.dat[b - 1], right);
            }
            a = a / 2;
            b = (b - 1) / 2;
        }
        (self.op)(left, right)
    }
}

trait Change { fn chmax(&mut self, x: Self); fn chmin(&mut self, x: Self); }
impl<T: PartialOrd> Change for T {
    fn chmax(&mut self, x: T) { if *self < x { *self = x; } }
    fn chmin(&mut self, x: T) { if *self > x { *self = x; } }
}

fn main() {
    // In order to avoid potential stack overflow, spawn a new thread.
    let stack_size = 104_857_600; // 100 MB
    let thd = std::thread::Builder::new().stack_size(stack_size);
    thd.spawn(|| solve()).unwrap().join().unwrap();
}

fn solve() {
    let out = std::io::stdout();
    let mut out = BufWriter::new(out.lock());
    macro_rules! puts {($($format:tt)*) => (let _ = write!(out,$($format)*););}
    #[allow(unused)]
    macro_rules! putvec {
        ($v:expr) => {
            for i in 0..$v.len() {
                puts!("{}{}", $v[i], if i + 1 == $v.len() {"\n"} else {" "});
            }
        }
    }
    input! {
        n: usize, q: usize,
        lrb: [(usize1, usize, i64); q],
    }
    let mut dst = DualSegTree::<Chmax>::new(&vec![1; n]);
    for &(l, r, b) in &lrb {
        dst.update(l, r, b);
    }
    let mut st = SegTree::new(n, min, 1 << 60);
    let mut v = vec![0; n];
    for i in 0..n {
        let a = dst.query(i);
        v[i] = a;
        st.update(i, dst.query(i));
    }
    for &(l, r, b) in &lrb {
        if st.query(l, r) != b {
            puts!("-1\n");
            return;
        }
    }
    putvec!(v);
}