#include <bits/stdc++.h>

#include <atcoder/lazysegtree>

#include <algorithm>
#include <cassert>
#include <vector>

template <class T>
bool chmax(T &a, const T &b) {
    if (a < b) {
        a = b;
        return true;
    }
    return false;
}

template <class T>
bool chmin(T &a, const T &b) {
    if (a > b) {
        a = b;
        return true;
    }
    return false;
}

template <class T>
T div_floor(T a, T b) {
    if (b < 0) a *= -1, b *= -1;
    return a >= 0 ? a / b : (a + 1) / b - 1;
}

template <class T>
T div_ceil(T a, T b) {
    if (b < 0) a *= -1, b *= -1;
    return a > 0 ? (a - 1) / b + 1 : a / b;
}

template <typename T>
struct CoordComp {
    std::vector<T> v;
    bool sorted;

    CoordComp() : sorted(false) {}

    int size() { return v.size(); }

    void add(T x) { v.push_back(x); }

    void build() {
        std::sort(v.begin(), v.end());

        v.erase(std::unique(v.begin(), v.end()), v.end());
        sorted = true;
    }

    int get_idx(T x) {
        assert(sorted);
        return lower_bound(v.begin(), v.end(), x) - v.begin();
    }

    T &operator[](int i) { return v[i]; }
};


#define For(i, a, b) for (int i = (int)(a); (i) < (int)(b); ++(i))
#define rFor(i, a, b) for (int i = (int)(a)-1; (i) >= (int)(b); --(i))
#define rep(i, n) For(i, 0, n)
#define rrep(i, n) rFor(i, n, 0)
#define fi first
#define se second

using namespace std;

using lint = long long;
using pii = pair<int, int>;
using pll = pair<lint, lint>;

using namespace atcoder;

constexpr int MAX = 1000'000'000;

int op(int a, int b) { return min(a, b); }

int e() { return MAX; }

int mapping(int f, int x) { return f ? f : x; }

int composition(int f, int g) { return f ? f : g; }

int id() { return 0; }

int main() {
    int n, q;
    scanf("%d%d", &n, &q);
    pair<int, pii> qs[q];
    rep(i, q) scanf("%d%d%d", &qs[i].se.fi, &qs[i].se.se, &qs[i].fi),
        --qs[i].se.fi;
    sort(qs, qs + q);

    lazy_segtree<int, op, e, int, mapping, composition, id> lst(n);
    for (auto [val, p] : qs) {
        auto [l, r] = p;
        lst.apply(l, r, val);
    }
    for (auto [val, p] : qs) {
        auto [l, r] = p;
        if (lst.prod(l, r) != val) {
            puts("-1");
            return 0;
        }
    }
    rep(i, n) printf("%d%c", lst.get(i), i == n - 1 ? '\n' : ' ');
}