use std::collections::BinaryHeap;

#[derive(Debug, Clone)]
struct SegmentTree<F, T> {
    n: usize,
    orgn: usize,
    unit: T,
    mem: Vec<T>,
    operator: F
}

impl<F, T> SegmentTree<F, T> where
T: std::fmt::Debug + Copy,
F: Fn(T, T) -> T
{
    fn new(n: usize, unit: T, operator: F) -> Self {
        let mut size = 1usize;
        while size < n { size *= 2; }
        Self {
            n: size,
            orgn: n,
            unit: unit,
            mem: vec![unit; size*2-1],
            operator: operator,
        }
    }

    fn find_closed(&self, l: usize, r: usize) -> T {
        self.find(l, r+1)
    }

    fn find(&self, l: usize, r: usize) -> T {
        self._find(l, r, 0, 0, self.n)
    }

    fn set(&mut self, pos: usize, val: T) {
        let mut pos = pos + self.n - 1;
        self.mem[pos] = val;
        while pos > 0 {
            pos = self._parent(pos);
            self.mem[pos] = (self.operator)(self.mem[self._left(pos)], self.mem[self._right(pos)]);
        }
    }

    fn get(&mut self, pos: usize) -> T {
        self.mem[pos + self.n - 1]
    }

    fn _find(&self, a: usize, b: usize, nodenum: usize, l: usize, r: usize) -> T {
        if r <= a || b <= l {
            return self.unit;
        } else if a <= l && r <= b {
            return self.mem[nodenum];
        }
        let left = self._find(a, b, self._left(nodenum), l, (l+r)/2);
        let right = self._find(a, b, self._right(nodenum), (l+r)/2, r);
        (self.operator)(left, right)
    }
    fn _left(&self, k: usize) -> usize {
        2*k+1
    }
    fn _right(&self, k: usize) -> usize {
        2*k+2
    }
    fn _parent(&self, k: usize) -> usize {
        (k-1)/2
    }
}

fn main() {
    let mut nq = String::new();
    std::io::stdin().read_line(&mut nq).ok();
    let nq: Vec<usize> = nq.trim().split_whitespace().map(|s| s.parse().unwrap()).collect();
    let n = nq[0];
    let q = nq[1];
    let queries = (0..q).map(|_| {
            let mut temp = String::new();
            std::io::stdin().read_line(&mut temp).ok();
            let temp: Vec<usize> = temp.trim().split_whitespace().map(|s| s.parse().unwrap()).collect();
            (temp[0]-1, temp[1], temp[2])
        })
        .collect::<Vec<_>>();

    let mut pque = BinaryHeap::new();
    let mut pop_targets = BinaryHeap::new();
    let mut result = vec![1e9 as usize; n];
    let mut qs = vec![vec![]; n+1];
    let mut qe = vec![vec![]; n+1];
    for &(l, r, b) in queries.iter() {
        qs[l].push(b);
        qe[r].push(b);
    }
    for i in 0..n {
        for &v in qs[i].iter() {
            pque.push(v);
        }
        for &v in qe[i].iter() {
            pop_targets.push(v);
        }
        while pque.len() > 0 && pop_targets.len() > 0 && pque.peek().unwrap() == pop_targets.peek().unwrap() {
            pque.pop();
            pop_targets.pop();
        }
        if let Some(&x) = pque.peek() {
            result[i] = x;
        }
    }
    let mut segtree = SegmentTree::new(n, 1e9 as usize, |x, y| x.min(y));
    for i in 0..n { segtree.set(i, result[i]); }
    if queries.iter().filter(|&&(l, r, b)| b != segtree.find_closed(l, r)).count() == 0 {
        println!("{}", result.iter().map(|&v| v.to_string()).collect::<Vec<_>>().join(" "));
    } else {
        println!("-1");
    }
}