#include <iostream>
#include <vector>
#include <algorithm>
#include <cmath>
#include <queue>
#include <string>
#include <map>
#include <set>
#include <stack>
#include <tuple>
#include <deque>
#include <array>
#include <numeric>
#include <bitset>
#include <iomanip>
#include <cassert>
#include <chrono>
#include <random>
#include <limits>
#include <iterator>
#include <functional>
#include <sstream>
#include <fstream>
#include <complex>
#include <cstring>
#include <unordered_map>
#include <unordered_set>
using namespace std;

// #pragma GCC optimize("O3")
// #pragma GCC optimize("unroll-loops")
// #pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,avx,avx2,tune=native")
// #pragma GCC target("avx512f,avx512dq,avx512cd,avx512bw,avx512vl")

using ll = long long;
constexpr int INF = 1001001001;
// constexpr int mod = 1000000007;
constexpr int mod = 998244353;

template<class T>
inline bool chmax(T& x, T y){
    if(x < y){
        x = y;
        return true;
    }
    return false;
}
template<class T>
inline bool chmin(T& x, T y){
    if(x > y){
        x = y;
        return true;
    }
    return false;
}

template<typename Monoid, typename OperatorMonoid = Monoid>
struct LazySegmentTree{
    using F = function<Monoid(Monoid, Monoid)>;
    using G = function<Monoid(Monoid, OperatorMonoid)>;
    using H = function<OperatorMonoid(OperatorMonoid, OperatorMonoid)>;

    int sz;
    vector<Monoid> data;
    vector<OperatorMonoid> lazy;
    const F f;
    const G g;
    const H h;
    const Monoid M1;            // モノイドの単位元
    const OperatorMonoid OM0;   // 作用素モノイドの単位元

    LazySegmentTree(int n, const F f, const G g, const H h, const Monoid &M1, const OperatorMonoid OM0)
        : f(f), g(g), h(h), M1(M1), OM0(OM0)
    {
        sz = 1;
        while(sz < n)   sz <<= 1;
        data.assign(sz << 1, M1);
        lazy.assign(sz << 1, OM0);
    }

    void set(int k, const Monoid &x){
        data[k + sz] = x;
    }

    void build(){
        for(int k = sz - 1; k > 0; --k){
            data[k] = f(data[k << 1], data[k << 1 | 1]);
        }
    }

    void propagate(int k){
        if(lazy[k] != OM0){
            if(k < sz){
                lazy[k << 1] = h(lazy[k << 1], lazy[k]);
                lazy[k << 1 | 1] = h(lazy[k << 1 | 1], lazy[k]);
            }
            data[k] = g(data[k], lazy[k]);
            lazy[k] = OM0;
        }
    }

    Monoid update(int a, int b, const OperatorMonoid &x, int k = 1, int l = 0, int r = -1){
        if(r == -1)     r = sz;
        propagate(k);
        if(r <= a || b <= l)    return data[k];
        else if(a <= l && r <= b){
            lazy[k] = h(lazy[k], x);
            propagate(k);
            return data[k];
        }
        else{
            return data[k] = f(update(a, b, x, k << 1, l, (l + r) >> 1),
                                update(a, b, x, k << 1 | 1, (l + r) >> 1, r));
        }
    }

    Monoid query(int a, int b, int k = 1, int l = 0, int r = -1){
        if(r == -1)     r = sz;
        propagate(k);
        if(r <= a || b <= l)    return M1;
        else if(a <= l && r <= b)   return data[k];
        else{
            return f(query(a, b, k << 1, l, (l + r) >> 1),
                        query(a, b, k << 1 | 1, (l + r) >> 1, r));
        }
    }

    Monoid operator[](const int &i){
        int k = 1, l = 0, r = sz, m;
        while(k < sz){
            propagate(k);
            k <<= 1;
            m = (l + r) >> 1;
            if(i + 1 <= m)  r = m;
            else { l = m; ++k; }
        }
        propagate(k);
        return data[k];
    }
};

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

    int N, Q;
    cin >> N >> Q;
    vector<tuple<int, int, int>> dat(Q);
    for(auto& [B, L, R] : dat){
        cin >> L >> R >> B;
        --L;
    }
    sort(begin(dat), end(dat));

    auto op = [](int l, int r){return min(l, r);};
    auto mapping = [](int l, int r){return r;};
    auto composition = [](int l, int r){return r;};
    LazySegmentTree<int, int> seg(N, op, mapping, composition, 1000000000, 0);
    for(auto& [b, l, r] : dat)  seg.update(l, r, b);
    
    for(auto& [b, l, r] : dat){
        if(seg.query(l, r) != b)    return puts("-1") & 0;
    }

    for(int i = 0; i < N; ++i){
        cout << seg[i] << (i == N - 1 ? '\n' : ' ');
    }

    return 0;
}