#include <atcoder/lazysegtree>
#include <algorithm>
#include <iostream>
using namespace std;
using namespace atcoder;
typedef pair<int, int> P;
typedef pair<int, P> PP;

const int INF = 1000000000;

struct S
{
    int x;
};

S op(S a, S b){
    return S{min(a.x, b.x)};
}

S e(){
    return S{INF};
}

struct F
{
    int f;
};

S mapping(F f, S a){
    if(f.f == 0) return a;
    return S{f.f};
}

F composition(F f, F g){
    if(f.f == 0) return g;
    return f;
}

F id(){
    return F{0};
}

int main()
{
    int n, q;
    cin >> n >> q;
    PP p[200005];
    for(int i = 0; i < q; i++){
        int l, r, b;
        cin >> l >> r >> b;
        l--;
        p[i] = PP(b, P(l, r));
    }
    sort(p, p + q);
    lazy_segtree<S, op, e, F, mapping, composition, id> seg(n);
    for(int i = 0; i < q; i++){
        seg.apply(p[i].second.first, p[i].second.second, F{p[i].first});
    }
    for(int i = 0; i < q; i++){
        if(seg.prod(p[i].second.first, p[i].second.second).x != p[i].first){
            cout << -1 << endl;
            return 0;
        }
    }
    for(int i = 0; i < n; i++){
        cout << seg.get(i).x;
        if(i < n - 1) cout << " ";
    }
    cout << endl;
}