#include <bits/stdc++.h>

#include <atcoder/lazysegtree>
using namespace std;
using namespace atcoder;
int op(int a, int b) { return min(a, b); }
int e() { return 1e9; }
int mapping(int f, int x) {
    if (f == -1) return x;
    return f;
}
int composition(int f, int g) {
    if (f == -1) return g;
    return f;
}
int id() { return -1; }
void fast_io() {
    ios_base::sync_with_stdio(false);
    cin.tie(nullptr);
}

int main() {
    fast_io();
    int n, q;
    cin >> n >> q;
    vector<tuple<int, int, int>> lrb;
    for (int i = 0; i < q; i++) {
        int l, r, b;
        cin >> l >> r >> b;
        l--;
        lrb.push_back({l, r, b});
    }
    vector<int> idx(q);
    iota(idx.begin(), idx.end(), 0);
    sort(idx.begin(), idx.end(),
         [&](int i, int j) { return get<2>(lrb[i]) < get<2>(lrb[j]); });
    lazy_segtree<int, op, e, int, mapping, composition, id> seg(n);
    for (int i : idx) {
        auto [l, r, b] = lrb[i];
        seg.apply(l, r, b);
    }
    for (auto [l, r, b] : lrb) {
        if (seg.prod(l, r) != b) {
            cout << -1 << endl;
            return 0;
        }
    }
    for (int i = 0; i < n; i++) {
        cout << seg.get(i) << " ";
    }
    cout << endl;
}