#include <bits/stdc++.h>
#include <atcoder/all>
using namespace std;
using namespace atcoder;
using ll=long long;
using ld=long double;
using S = long long;
using F = long long;
ll inf=1000000000;
const S INF = inf;
const F ID = inf+1;
S op(S a, S b){ return std::min(a, b); }
S e(){ return INF; }
S mapping(F f, S x){ return (f == ID ? x : f); }
F composition(F f, F g){ return (f == ID ? g : f); }
F id(){ return ID; }
ld pie=3.141592653589793;
ll mod=1000000007;
int main(){
    ll n,q;
    cin >> n >> q;
    vector<ll>l(q),r(q),b(q);
    vector<pair<ll,pair<ll,ll>>>p(q);
    for (ll i = 0; i < q; i++)
    {
        cin >> l[i] >> r[i] >> b[i];
        l[i]--;
        p[i]={b[i],{l[i],r[i]}};
    }
    sort(p.begin(),p.end());
    vector<ll>v(n,inf);
    atcoder::lazy_segtree<S, op, e, F, mapping, composition, id> seg(v);
    for (ll i = 0; i < p.size(); i++)
    {
        seg.apply(p[i].second.first,p[i].second.second,p[i].first);
    }
    bool ok=true;
    for (ll i = 0; i < p.size(); i++)
    {
        ll x=seg.prod(p[i].second.first,p[i].second.second);
        if (x!=p[i].first)
        {
            ok=false;
            break;
        }
    }
    if (ok)
    {
        vector<ll>a(n);
        for (ll i = 0; i < n; i++)
        {
            a[i]=seg.get(i);
        }
        for (ll i = 0; i < n; i++)
        {
            cout << a[i];
            if (i<n-1)
            {
                cout << ' ';
            }
        }
        cout << endl;
    }else{
        cout << -1 << endl;
    }
    
}