#include <bits/stdc++.h>
using namespace std;
#define rep(i, n) for (int i = 0; i < n; i++)
#define rep2(i, x, n) for (int i = x; i <= n; i++)
#define rep3(i, x, n) for (int i = x; i >= n; i--)
#define each(e, v) for (auto &e : v)
#define pb push_back
#define eb emplace_back
#define all(x) x.begin(), x.end()
#define rall(x) x.rbegin(), x.rend()
#define sz(x) (int)x.size()
using ll = long long;
using pii = pair<int, int>;
using pil = pair<int, ll>;
using pli = pair<ll, int>;
using pll = pair<ll, ll>;
const int MOD = 1000000007;
// const int MOD = 998244353;
const int inf = (1 << 30) - 1;
const ll INF = (1LL << 60) - 1;
template <typename T>
bool chmax(T &x, const T &y) {
    return (x < y) ? (x = y, true) : false;
}
template <typename T>
bool chmin(T &x, const T &y) {
    return (x > y) ? (x = y, true) : false;
}

struct io_setup {
    io_setup() {
        ios_base::sync_with_stdio(false);
        cin.tie(NULL);
        cout << fixed << setprecision(15);
    }
} io_setup;

int main() {
    int N, Q;
    cin >> N >> Q;

    vector<int> l(Q), r(Q), b(Q);

    map<int, vector<int>> mp;

    rep(i, Q) {
        cin >> l[i] >> r[i] >> b[i];
        l[i]--;
        mp[-b[i]].eb(i);
    }

    set<int> s;
    rep(i, N) s.emplace(i);
    vector<int> ans(N, 1000000000);

    each(e, mp) {
        set<int> tmp;
        each(i, e.second) {
            auto it = s.lower_bound(l[i]);
            if (it == end(s) || *it >= r[i]) {
                auto it2 = tmp.lower_bound(l[i]);
                if (it2 == end(tmp) || *it2 >= r[i]) {
                    cout << "-1\n";
                    return 0;
                }
            }
            for (; it != end(s) && *it < r[i]; it = s.erase(it)) {
                ans[*it] = b[i];
                tmp.emplace(*it);
            }
        }
    }

    rep(i, N) cout << ans[i] << (i == N - 1 ? '\n' : ' ');
}