#include <bits/stdc++.h>
#define rep(i, n) for (int i = 0; i < n; ++i)
typedef long long ll;
using namespace std;

int main() {
    int N, Q;
    cin >> N >> Q;
    vector<tuple<int, int, int>> vt(Q);
    rep(i, Q) {
        int l, r, b;
        cin >> l >> r >> b;
        l--, r--;
        vt[i] = {l, -r, b};
    }
    sort(vt.begin(), vt.end());

    int i = 0;
    vector<int> ans(N, 1e9);
    for (auto &[l, r, b] : vt) {
        r = -r;
        bool flag = false;
        for (int j = max(l, i); j <= r; ++j) {
            i++;
            if (ans[j] > b) {
                ans[j] = b;
                flag = true;
                break;
            }
        }
        if (!flag) {
            cout << -1 << endl;
            return 0;
        }
    }

    rep(i, N) {
        if (i != 0) cout << " ";
        cout << ans[i];
    }
    cout << endl;

    return 0;
}