#include <bits/stdc++.h>
using namespace std;
using ll = long long;

template <class T>
struct SegmentTree {
    SegmentTree(int n) : n(n) {
        for (m = 2; m < n; m *= 2);
        t = vector<T>(m + n + n % 2);
    }
    T &operator[](int i) {
        return t[m + i];
    }
    const T &root() const {
        return t[1];
    }
    void build() {
        for (int i = (n - 1 + m) / 2; i > 0; i--) t[i] = t[i * 2] * t[i * 2 + 1];
    }
    void update(int i, const T &o) {
        for (t[i += m] = o; i /= 2, i > 0;) t[i] = t[i * 2] * t[i * 2 + 1];
    }
    T query(int l, int r) {
        T o0, o1;
        for (l += m, r += m; l < r; l /= 2, r /= 2) {
            if (l & 1) o0 = o0 * t[l++];
            if (r & 1) o1 = t[--r] * o1;
        }
        return o0 * o1;
    }
    vector<T> t;
    int n, m;
};
struct Min {
    constexpr Min() : v(1 << 30) {}
    Min(int v) : v(v) {}
    Min operator*(const Min &o) const {
        return min(v, o.v);
    }
    int v;
};

struct P {
    bool operator<(const P &p) const {
        return i < p.i;
    }
    int i, b, s;
};

struct Q {
    int l, r, b;
};

int main() {
    ios::sync_with_stdio(false);
    cin.tie(0);

    int n, q;
    cin >> n >> q;

    vector<P> p(q * 2);
    vector<Q> x(q);
    for (int i = 0; i < q; i++) {
        int l, r, b;
        cin >> l >> r >> b;
        l--;

        p[i * 2 + 0] = { l, b, 0 };
        p[i * 2 + 1] = { r, b, 1 };
        x[i] = { l, r, b };
    }
    sort(p.begin(), p.end());

    SegmentTree<Min> st(n);

    multiset<int> ms;
    int j = 0;
    for (int i = 0; i < n; i++) {
        while (j < q * 2 && p[j].i <= i) {
            if (p[j].s == 0) {
                ms.insert(p[j++].b);
            } else {
                ms.erase(ms.find(p[j++].b));
            }
        }
        auto it = ms.end();
        int t = 1;
        if (!ms.empty()) t = *--it;
        st[i].v = t;
    }
    st.build();

    for (int i = 0; i < q; i++) {
        const auto &[l, r, b] = x[i];
        if (st.query(l, r).v != b) {
            cout << -1 << endl;
            exit(0);
        }
    }
    for (int i = 0; i < n; i++) {
        cout << st[i].v << " \n"[i == n - 1];
    }

    return 0;
}