#include <bits/stdc++.h>
#include <atcoder/all>

#pragma GCC target("avx2")
#pragma GCC optimize("O3")
#pragma GCC optimize("unroll-loops")

using namespace atcoder;
using namespace std;

struct S {int x;};
struct F {int y;};

constexpr int inf = 1000000000;
const F ID = F{222};

S op(S l, S r) {
	return S{min(l.x, r.x)};
}

S e() {
	return S{inf};
}

S mapping(F f, S s) {
	if( f.y == ID.y ) return s;
	else return S{f.y};
}

F composition(F f, F g) {
	if( f.y == ID.y ) return F{g};
	else return F{f};
}

F id() {
	return ID;
}

int main() {
    
    int N, Q; cin >> N >> Q;
    bool ng = false;
    vector<S> v(N, S{inf});
    vector<tuple<int, int, int>> query(Q);
    for( int i = 0; i < Q; i++ ) {
        int l, r, b; cin >> l >> r >> b;
        query[i] = make_tuple(b, l, r);
    }
    
    sort(query.begin(), query.end());
    lazy_segtree<S, op, e, F, mapping, composition, id> ls(v);
    
    for( int i = 0; i < Q; i++ ) {
        int b, l, r;
        tie(b, l, r) = query[i];
        ls.apply(l-1, r, F{b});
    }
    
    for( int i = 0; i < Q; i++ ) {
        int b, l, r;
        tie(b, l, r) = query[i];
        S res = ls.prod(l-1, r);
        if( res.x != b ) ng = true;
    }
    
    if(ng) {
        cout << -1 << endl;
    }else {
        for( int i = 0; i < N; i++ ) {
            S res = ls.get(i);
            if( i > 0 ) cout << ' ';
            cout << res.x;
        }
        cout << endl;
    }
    
}