#include <bits/stdc++.h>
using namespace std;
typedef long long int ll;


int main(){
    ll n,q;
    cin >> n >> q;
    vector<vector<ll>> query;
    vector<ll> ans(n);
    for(ll i = 0;i < q;i++){
        ll l,r,v;
        cin >> l >> r >> v;
        l--;
        r--;
        query.push_back({l,r,v});
        for(ll j = l;j <= r;j++){
            ans[j] = v;
        }
    }
    for(ll i = 0;i < q;i++){
        ll l = query[i][0], r = query[i][1],v = query[i][2];
        ll mini = 1e10;
        for(ll j = l;j <= r;j++){
            mini = min<ll>(mini, ans[j]);
        }
        if(mini != v){
            cout << -1 << "\n";
            return 0;
        }
    }
    for(ll i = 0;i < ans.size() - 1;i++){
        cout << ans[i] << " ";
    }
    cout << ans[ans.size() - 1] << "\n";
    return 0;
}