#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 + 1);

    // unused = {1..n}
    for (int i = 1; i <= n; i++)
        unused.insert(i);

    for (int i = 0; i < q; i++) {
        int l, r, b;
        scanf("%d %d %d", &l, &r, &b);  // gi? nguyên 1-based
        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) {
            // không có ph?n t? unused trong ?o?n [l, r]
            if (used.size() == 0) {
                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 = 1; i <= n; i++)
        cout << ans[i] << " \n"[i == n];

    return 0;
}