#include <bits/stdc++.h>
#include <atcoder/lazysegtree>
#define int long long
using namespace std;
using namespace atcoder;
using vec_int = vector<int>;
using vec_ii = vector<vec_int>;
using vec_iii = vector<vec_ii>;
using vec_iiii = vector<vec_iii>;
using P = pair<int,int>;
using T = tuple<int,int,int>;
using ll = long long;
using ld = long double;
#define rep(i, n) for(int i = 0; i < (int)(n); i++)

void cout_line(vector<int> &a){
    for(int i=0;i<a.size();i++){
        if(i<a.size()-1){
            cout<<a.at(i)<<" ";
        }else{
            cout<<a.at(i)<<endl;
        }
    }
}

int op(int a, int b){
    return min(a, b);
}
int e() {
    return INT_MAX;
}
int mapping(int f, int x){
    return max(f, x);
}
int composition(int a, int b){
    return max(a, b);
}

int id(){
    return -1;
}




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

    int N, Q; cin>>N>>Q;
    vec_int l(Q), r(Q), B(Q);
    rep(i, Q)cin>>l.at(i)>>r.at(i)>>B.at(i);
    vector<T> Qs(Q);
    rep(i, Q){
        Qs.at(i) = make_tuple(B.at(i), l.at(i), r.at(i));
    }
    sort(Qs.begin(), Qs.end());
    reverse(Qs.begin(), Qs.end());

    vec_int a(N, -1);
    lazy_segtree<int, op, e, int, mapping, composition, id> seg(a);

    rep(i, Q){
        int b, L, R; tie(b, L, R) = Qs.at(i);
        L--; R--;
        int temp = seg.prod(L, R+1);
        /*
        cout<<i<<" "<<L<<" "<<R<<" "<<temp<<endl;
        for(int j=0;j<5;j++){
            cout<<"i="<<i<<" j="<<j<<" "<<seg.get(j)<<endl;
        }
        */
        if(temp!=-1&&temp>b){
            cout<<-1<<endl;
            return 0;
        }
        seg.apply(L, R+1, b);
    }
    vec_int ans(N);
    rep(i,N){
        int num = seg.get(i);
        if(num==-1)num=4545;
        ans.at(i) = num;
    }
    cout_line(ans);






    return 0;
}