const INF: usize = 1usize << 60;
const UNIT: usize = 1e9 as usize;

#[derive(Debug, Clone)]
struct LazySegmentTree<F, G, H, T, U> {
    n: usize,
    orgn: usize,
    unit: T,
    mem: Vec<T>,
    lazy_unit: U,
    lazy: Vec<U>,
    operator: F,
    mapper: G,
    composer: H,
}

impl<F, G, H, T, U> LazySegmentTree<F, G, H, T, U> where
T: std::fmt::Debug + Copy,
U: std::fmt::Debug + std::cmp::PartialEq + Copy,
F: Fn(T, T) -> T,
G: Fn(T, U) -> T,
H: Fn(U, U) -> U,
{
    fn new(n: usize, unit: T, lazy_unit: U, operator: F, mapper: G, composer: H) -> Self {
        let mut size = 1usize;
        while size < n { size *= 2; }
        Self {
            n: size,
            orgn: n,
            unit: unit,
            mem: vec![unit; size*2-1],
            lazy_unit: lazy_unit,
            lazy: vec![lazy_unit; size*2-1],
            operator: operator,
            mapper: mapper,
            composer: composer,
        }
    }

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

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

    fn update_closed(&mut self, left: usize, right: usize, val: U) {
        self.update(left, right+1, val);
    }

    fn update(&mut self, left: usize, right: usize, val: U) {
        self._update(left, right, val, 0, 0, self.n);
    }

    fn get(&mut self, pos: usize) -> T {
        self.find_closed(pos, pos)
    }

    fn _evaluate(&mut self, k: usize) {
        if self.lazy[k] == self.lazy_unit { return; }
        if k < self.n-1 {
            let left = self._left(k);
            let right = self._right(k);
            self.lazy[left] = (self.composer)(self.lazy[left], self.lazy[k]);
            self.lazy[right] = (self.composer)(self.lazy[right], self.lazy[k]);
        }
        self.mem[k] = (self.mapper)(self.mem[k], self.lazy[k]);
        self.lazy[k] = self.lazy_unit;
    }
    fn _find(&mut self, a: usize, b: usize, nodenum: usize, l: usize, r: usize) -> T {
        self._evaluate(nodenum);
        if r <= a || b <= l {
            self.unit
        } else if a <= l && r <= b {
            self.mem[nodenum]
        } else {
            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 _update(&mut self, a: usize, b: usize, x: U, nodenum: usize, l: usize, r: usize) {
        self._evaluate(nodenum);
        if a <= l && r <= b {
            self.lazy[nodenum] = (self.composer)(self.lazy[nodenum], x);
            self._evaluate(nodenum);
        } else if a < r && l < b {
            self._update(a, b, x, self._left(nodenum), l, (l + r) / 2);
            self._update(a, b, x, self._right(nodenum), (l + r) / 2, r);
            self.mem[nodenum] = (self.operator)(self.mem[self._left(nodenum)], self.mem[self._right(nodenum)]);
        }
    }
    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 mut 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]-1, temp[2])
        })
        .collect::<Vec<_>>();

    queries.sort_by_key(|&(_, _, v)| v);
    let mut segtree = LazySegmentTree::new(n, INF, INF, |x, y| x.min(y), |x, y| y, |x, y| if y == INF { x } else { y });
    for &(l, r, b) in queries.iter() {
        segtree.update_closed(l, r, b);
    }
    if queries.iter().filter(|&&(l, r, b)| b != segtree.find_closed(l, r)).count() > 0 {
        println!("-1");
    } else {
        println!("{}", (0..n).map(|i| segtree.get(i).min(UNIT).to_string()).collect::<Vec<_>>().join(" "));
    }
}