#include "bits/stdc++.h"
#include "atcoder/all"
using namespace std;
using namespace atcoder;
//using mint = modint1000000007;
//const int mod = 1000000007;
//using mint = modint998244353;
//const int mod = 998244353;
const int INF = 1e9;
//const long long LINF = 1e18;
//const bool debug = false;
#define rep(i, n) for (int i = 0; i < (n); ++i)
#define rep2(i,l,r)for(int i=(l);i<(r);++i)
#define rrep(i, n) for (int i = (n-1); i >= 0; --i)
#define rrep2(i,l,r)for(int i=(r-1);i>=(l);--i)
#define all(x) (x).begin(),(x).end()
#define allR(x) (x).rbegin(),(x).rend()
#define endl "\n"
#define P pair<int,int>
template<typename A, typename B> inline bool chmax(A & a, const B & b) { if (a < b) { a = b; return true; } return false; }
template<typename A, typename B> inline bool chmin(A & a, const B & b) { if (a > b) { a = b; return true; } return false; }
using S = int;
using F = int;

S op(S a, S b) { return std::min(a, b); }
S e() { return INF; }
S mapping(F f, S x) { return (f == INF ? x : f); }
F composition(F f, F g) { return (f == INF ? g : f); }
F id() { return INF; }

int main() {
	ios::sync_with_stdio(false);
	cin.tie(nullptr);
	int n, q; cin >> n >> q;
	vector<pair<int, P>>v(q);
	rep(i, q) {
		int l, r, b; cin >> l >> r >> b;
		l--; r--;
		v[i] = { b,{l,r} };
	}
	sort(all(v));
	vector<int>vs(n, INF);
	lazy_segtree<S, op, e, F, mapping, composition, id> seg(vs);
	rep(i, q) {
		int x = v[i].first;
		int l = v[i].second.first;
		int r = v[i].second.second;
		seg.apply(l, r + 1, x);
	}
	rep(i, q) {
		int x = v[i].first;
		int l = v[i].second.first;
		int r = v[i].second.second;
		int y = seg.prod(l, r + 1);
		if (x != y) {
			cout << -1 << endl;
			return 0;
		}
	}
	rep(i, n) {
		if (0 != i)cout << " ";
		cout << seg.get(i);
	}
	cout << endl;
	return 0;
}