#![allow(unused_imports)]
#![allow(non_snake_case, unused)]

// ---------- begin input macro ----------
// https://qiita.com/tanakh/items/0ba42c7ca36cd29d0ac8 より
macro_rules! input {
    (source = $s:expr, $($r:tt)*) => {
        let mut iter = $s.split_whitespace();
        let mut next = || { iter.next().unwrap() };
        input_inner!{next, $($r)*}
    };
    ($($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:ty) => {
        $next().parse::<$t>().expect("Parse error")
    };
}
// ---------- end input macro ----------


use std::cmp::*;
use std::collections::*;
use std::ops::*;
use std::marker::*;
 
const INF: i64 = std::i64::MAX/100;
const MOD: i64 = 1_000_000_007;
// const MOD: i64 = 998_244_353;

// ---------- begin lazy segment tree ----------
// https://yukicoder.me/submissions/379658 より
pub trait TE {
    type T: Clone;
    type E: Clone;
    fn fold(l:Self::T, r:Self::T) -> Self::T;
    fn eval(p:Self::T, x:Self::E) -> Self::T;
    fn merge(f:Self::E, g:Self::E) -> Self::E;
    fn e() -> Self::T;
    fn id() -> Self::E;
}

pub struct LazySegmentTree<R: TE> {
    size: usize,
    bit: usize,
    a: Vec<(R::T, R::E)>,
}

impl <R: TE> LazySegmentTree<R> {
    pub fn new(n: usize) -> LazySegmentTree<R> {
        let mut bit = 0;
        while (1 << bit) < n {
            bit += 1;
        }
        LazySegmentTree {
            size: 1 << bit,
            bit: bit,
            a: vec![(R::e(), R::id()); 2 << bit],
        }
    }
    pub fn build_by(z: &[R::T]) -> LazySegmentTree<R> {
        let n = z.len();
        let mut bit = 0;
        while (1 << bit) < n {
            bit += 1;
        }
        let mut a = vec![(R::e(), R::id()); 2 << bit];
        for (a, z) in a[(1 << bit)..].iter_mut().zip(z.iter()) {
            a.0 = z.clone();
        }
        for i in (1..(1 << bit)).rev() {
            let l = R::eval(a[2 * i].0.clone(), a[2 * i].1.clone());
            let r = R::eval(a[2 * i + 1].0.clone(), a[2 * i + 1].1.clone());
            a[i].0 = R::fold(l, r);
        }
        LazySegmentTree {
            size: 1 << bit,
            bit : bit,
            a: a,
        }
    }
    fn eval(&self, k: usize) -> R::T {
        R::eval(self.a[k].0.clone(), self.a[k].1.clone())
    }
    fn propagate(&mut self, x: usize) {
        let x = x + self.size;
        for i in (1..(self.bit + 1)).rev() {
            let k = x >> i;
            self.a[2 * k].1 = R::merge(self.a[2 * k].1.clone(), self.a[k].1.clone());
            self.a[2 * k + 1].1 = R::merge(self.a[2 * k + 1].1.clone(), self.a[k].1.clone());
            self.a[k].1 = R::id();
            self.a[k].0 = R::fold(self.eval(2 * k), self.eval(2 * k + 1));
        }
    }
    fn save(&mut self, x: usize) {
        let x = x + self.size;
        for i in 1..(self.bit + 1) {
            let k = x >> i;
            self.a[k].0 = R::fold(self.eval(2 * k), self.eval(2 * k + 1));
        }
    }
    pub fn update(&mut self, l: usize, r: usize, op: R::E) {
        self.propagate(l);
        self.propagate(r - 1);
        let mut x = l + self.size;
        let mut y = r + self.size;
        while x < y {
            if x & 1 == 1 {
                self.a[x].1 = R::merge(self.a[x].1.clone(), op.clone());
                x += 1;
            }
            if y & 1 == 1 {
                y -= 1;
                self.a[y].1 = R::merge(self.a[y].1.clone(), op.clone());
            }
            x >>= 1;
            y >>= 1;
        }
        self.save(l);
        self.save(r - 1);
    }
    pub fn find(&mut self, l: usize, r: usize) -> R::T {
        self.propagate(l);
        self.propagate(r - 1);
        let mut x = l + self.size;
        let mut y = r + self.size;
        let mut p = R::e();
        let mut q = R::e();
        while x < y {
            if x & 1 == 1 {
                p = R::fold(p, self.eval(x));
                x += 1;
            }
            if y & 1 == 1 {
                y -= 1;
                q = R::fold(self.eval(y), q);
            }
            x >>= 1;
            y >>= 1;
        }
        R::fold(p, q)
    }
}


struct R;
impl TE for R {
    type T = (i64,usize);
    type E = (i64,usize);
    fn fold(l: Self::T, r: Self::T) -> Self::T {
        min(l,r)
    }
    fn eval(p: Self::T, x: Self::E) -> Self::T {
        if x.1>p.1 {
            x
        }
        else {
            p
        }
    }
    fn merge(f: Self::E, g: Self::E) -> Self::E {
        if f.1>g.1 {
            f
        }
        else {
            g
        }
    }
    fn e() -> Self::T {
        (1_000_000_000,0)
    }
    fn id() -> Self::E {
        (1_000_000_000,0)
    }
}
// ---------- end lazy segment tree ----------

fn main() {
    input! {
        n: usize,
        q: usize,
        lrb: [(usize,usize,i64);q],
    }
    let mut seg = LazySegmentTree::<R>::new(n);
    for i in 0..n {
        seg.update(i,i+1,(1_000_000_000,0));
    }
    let mut v = vec![];
    for &(l,r,b) in &lrb {
        v.push((b,l-1,r-1));
    }
    v.sort();
    let mut idx = 1;
    for &(b,l,r) in &v {
        seg.update(l,r+1,(b,idx));
        idx += 1;
    }
    for &(b,l,r) in &v {
        let v = seg.find(l,r+1);
        if b!=v.0 {
            println!("-1");
            return;
        }
    }
    for i in 0..n-1 {
        print!("{} ",seg.find(i,i+1).0);
    }
    println!("{}",seg.find(n-1,n).0);
}