#include <bits/stdc++.h>
#include <bits/extc++.h>
using namespace __gnu_pbds;
using namespace std;
#pragma GCC optimize("Ofast")
#pragma GCC optimize ("unroll-loops")
#pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,avx,tune=native")
#define ff first
#define sc second
#define pb push_back
#define ll long long
#define pll pair<ll, ll>
#define pii pair<int, int>
#define ull unsigned long long
#define all(x) (x).begin(),(x).end()
#define rall(x) (x).rbegin(),(x).rend()
mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
mt19937_64 rngl(chrono::steady_clock::now().time_since_epoch().count());
// #define int long long
// #define int unsigned long long
// #define ordered_set(T) tree<T, null_type, less<T>, rb_tree_tag, tree_order_statistics_node_update>
// #define ordered_multiset(T) tree<T, null_type, less_equal<T>, rb_tree_tag, tree_order_statistics_node_update>
const ll mod = 1e9 + 7;
// const ll mod = 998244353;
const ll inf = 1e9;
const ll biginf = 1e18;
const int maxN = 1e5 + 15;
int n, q, lb[maxN], rb[maxN];
void impossible() {
for (int i = 1; i <= n; i++)
cout << -1 << ' ';
exit(0);
}
void solve() {
cin >> n >> q;
for (int i = 1; i <= n; i++) lb[i] = 1, rb[i] = n;
vector<int> vec[n + 5], qs[n + 5];
for (int i = 1; i <= q; i++) {
int l, r, v; cin >> l >> r >> v; l++; r++; v++;
vec[l].pb(v); vec[r + 1].pb(-v);
lb[v] = max(lb[v], l); rb[v] = min(rb[v], r);
}
multiset<int> st;
for (int i = 1; i <= n; i++) {
if (lb[i] > rb[i]) impossible();
for (int j : vec[i]) {
if (j >= 0) st.insert(j);
else st.erase(st.find(-j));
}
qs[(st.empty() ? 1 : *st.rbegin())].pb(i);
}
st.clear(); int ans[n + 1];
for (int i = 1; i <= n; i++) {
for (int j : qs[i]) st.insert(j);
auto it = st.lower_bound(lb[i]);
if (it == st.end() || *it > rb[i]) impossible();
ans[*it] = i; st.erase(it);
}
for (int i = 1; i <= n; i++)
cout << ans[i] - 1 << ' ';
}
int32_t main() {
// #ifndef ONLINE_JUDGE
// freopen("input.txt", "r", stdin);
// freopen("output.txt", "w", stdout);
// #endif
ios_base::sync_with_stdio(false);
cin.tie(nullptr); cout.tie(nullptr);
int t = 1;
// cin >> t;
while (t--) {
solve();
cout << '\n';
}
return 0;
}
