#include<bits/stdc++.h>

using namespace std;

#define endl "\n"
#define all(v) v.begin(), v.end()

const int N = 2e5 + 10;

int n,q;

int main()
{
    scanf("%d %d",&n,&q);
    vector<array<int,3>> query(q);
    set<int> unused;
    set<int> used;
    vector<int> ans(n);
    for(int i = 0;i < n;i ++ ) unused.insert(i);
    for(int i = 0;i < q;i ++ )
    {
        int l,r,b;
        scanf("%d %d %d",&l,&r,&b);
        l --, r --;
        query[i] = {b,l,r};
    }
    sort(all(query));
    reverse(all(query));
    int prev = -1;
    for(auto [b,l,r] : query)
    {
        if(b != prev)
        {
            prev = b;
            used.clear();
        }
        auto itr = unused.lower_bound(l);
        if(itr == unused.end() || *itr > r)
        {
            auto itr2 = used.lower_bound(l);
            if(itr2 == used.end())
            {
                cout << "-1" << endl;
                return 0;
            }
        }
        else
        {
            while(itr != unused.end() && *itr <= r)
            {
                ans[*itr] = b;
                used.insert(*itr);
                itr = unused.erase(itr);
            }
        }
    }
    for(auto i : unused) ans[i] = int(1e9);
    for(int i = 0;i < n;i ++ ) cout << ans[i] << " \n"[i == n - 1];
    return 0;
}