#include <bits/stdc++.h>
using namespace std;
typedef int ll;
typedef vector<int> vl;
typedef vector<vl> vvl;
#define all(x) x.begin(), x.end()
#define pb push_back
#define f first
#define s second
const char nd = '\n';
const int infi = 1e9;
struct queries {
ll l, r, mini;
};
struct nodo {
ll l, r;
ll mini;
nodo *left, *right;
};
nodo *st;
void start(nodo *yo, vl &a) {
if (yo->l == yo->r) {
yo->mini = a[yo->l];
return;
}
ll mid = (yo->l + yo->r) / 2;
yo->left = new nodo({yo->l, mid, 0, NULL, NULL});
yo->right = new nodo({mid + 1, yo->r, 0, NULL, NULL});
start(yo->left, a);
start(yo->right, a);
yo->mini = min(yo->left->mini, yo->right->mini);
}
ll query(nodo *c, ll l, ll r) {
if (r < c->l || c->r < l) return infi;
if (l <= c->l && c->r <= r) return c->mini;
return min(query(c->left, l, r), query(c->right, l, r));
}
signed main() {
ios_base::sync_with_stdio(0);
cin.tie(0);
cout.tie(0);
int n, q;
cin >> n >> q;
vector<queries> que;
vector<pair<int, int> > might(n, make_pair(-1, -1)),
need(n, make_pair(-1, -1));
vl res(n, -1);
ll l, r, mini;
while (q--) {
cin >> l >> r >> mini;
que.pb({l, r, mini});
if (need[mini].f == -1) {
need[mini] = make_pair(l, r);
} else {
need[mini].f = max(need[mini].f, l);
need[mini].s = min(need[mini].s, r);
}
if (might[mini].f == -1) {
might[mini] = make_pair(l, r);
} else {
might[mini].f = min(might[mini].f, l);
might[mini].s = max(might[mini].s, r);
}
}
set<ll> have, marked;
for (ll i = 0; i < n; i++) have.insert(i), marked.insert(i);
set<ll>::iterator it, it2;
for (ll i = n - 1; i >= 0; i--) {
if (need[i].f == -1) continue;
it = marked.lower_bound(need[i].f);
if (need[i].f > need[i].s || it == marked.end() || *it > need[i].s) {
for (auto v : res) cout << -1 << " ";
cout << nd;
return 0;
}
res[*it] = i;
marked.erase(it);
have.erase(i);
while (true) {
it = marked.lower_bound(might[i].f);
if (it == marked.end() || *it > might[i].s) break;
it2 = have.lower_bound(i);
if (it2 == have.end()) {
for (auto v : res) cout << -1 << " ";
cout << nd;
return 0;
}
res[*it] = *it2;
marked.erase(it);
have.erase(it2);
}
}
for (auto &v : res) {
if (v == -1) {
v = *(have.begin());
have.erase(have.begin());
}
}
// for (auto v : res) cout << v << " ";
// cout << nd;
nodo *st = new nodo({0, n - 1, 0, NULL, NULL});
start(st, res);
for (auto v : que) {
if (query(st, v.l, v.r) != v.mini) {
for (auto v : res) cout << -1 << " ";
cout << nd;
return 0;
}
}
for (auto v : res) cout << v << " ";
cout << nd;
}
