#pragma GCC optimize("O3,unroll-loops")
#pragma GCC target("avx2,bmi,bmi2,lzcnt,popcnt")
#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
using namespace std;
using namespace __gnu_pbds;
template <class T>
using ordered_set = tree<T, null_type, less<T>, rb_tree_tag, tree_order_statistics_node_update>;
#define endl '\n';
#define fastio ios_base::sync_with_stdio(false); cin.tie(0); cout.tie(0);
#define py cout << "YES" << endl;
#define pn cout << "NO" << endl;
#define pb push_back
#define int long long
typedef long double lld;
#define double lld
typedef long long ll;
typedef unsigned long long ull;
const ll inf = 1e18;
const ll mod = 1e9+7;
const int N = 2e5;
vector<int>primes = {2,3,5,7,11,13,17,19,23,29,31,37,41,43,47,53,59,61,67,71,73,79,83,89,97};
// Check for queue, priorioty_queue, stack, ordered_set solutions
// stack => LIFO (whatever goes in last comes out last)
// queue => FIFO (whatever goes in first comes out first)
// priority_queue => Dynamic queries of minimum/maximum
// ordered_set => set in vector form
//[order_of_key(k) gives number of elements less than k, while find_by_order(i) gives i^th element]
// To comment multiple lines : ctrl + /
// To find and replace : ctrl+H
void judge(){
srand(time(NULL));
#ifndef ONLINE_JUDGE
freopen("1.txt","r",stdin);
freopen("2.txt","w",stdout);
freopen("Error.txt", "w", stderr);
#define debug(x...) cerr << #x <<" = "; _print(x); cerr << endl;
#else
#define debug(x...)
#endif
}
void usaco(string s) {
freopen((s + ".in").c_str(),"r",stdin);
freopen((s + ".out").c_str(),"w",stdout);
}
struct node {
int sum; // The sum of the range (used for sum queries)
node(int x = 0){
sum = x;
}
};
void bad(int n){
for(int i = 0;i<n-1;i++){
cout << -1 << ' ';
}
cout << -1;
}
class SegTree{
int n; vector<node>t; vector<int>a;
node unite(node a, node b){ // Make changes here
return node(min(a.sum,b.sum));
}
private:
#define mid (start+end)/2
#define lc x+1
#define rc 2*(mid-start+1) + x
void build(int x, int start, int end){ // Make changes here
if(start==end){
t[x] = node(a[start]);
return;
}
build(lc,start,mid);
build(rc,mid+1,end);
t[x] = unite(t[lc],t[rc]);
return;
}
void update(int x, int start, int end, int idx, int val){
if(start==end){
t[x] = node(val); return;
}
if(idx<=mid){
update(lc,start,mid,idx,val);
}
else{
update(rc,mid+1,end,idx,val);
}
t[x] = unite(t[lc],t[rc]); return;
}
node query(int x, int start, int end, int l, int r){
if(l<=start and end<=r){
return t[x];
}
if(r<=mid){
return query(lc,start,mid,l,r);
}
else if(mid<l){
return query(rc,mid+1,end,l,r);
}
else{
return unite(query(lc,start,mid,l,r),query(rc,mid+1,end,l,r));
}
}
public:
SegTree(vector<int>& tmp){
n = tmp.size();
t.resize(2 * n);
a = tmp;
build(0, 0, n - 1);
}
node query(int l, int r){
return query(0, 0, n - 1, l, r);
}
void update(int pos, int val){ // Make changes here
update(0, 0, n - 1, pos, val);
}
};
signed main(){
fastio; //judge();
int n,q; cin >> n >> q;
vector<pair<int,int>>a(n,{-1,inf});
vector<vector<pair<int,int>>>all(n);
set<int>fs; set<int>others; set<int>fs2;
vector<bool>vis(n,false);
while(q--){
int l,r,x; cin >> l >> r >> x;
all[x].pb({l,r});
a[x].first = max(a[x].first,l);
a[x].second = min(a[x].second,r);
vis[x] = true;
}
for(int i = 0;i<n;i++){
if(vis[i]){
fs.insert(i);
}
else{
others.insert(i);
}
}
// Put all the numbers in their "smaller" bound limits
vector<int>tmp(n,-1);
vector<bool>remove(n,false);
vector<vector<int>>add(n);
vector<vector<int>>sub(n);
for(int i = 0;i<n;i++){
int curr_l = -1, curr_r = -1;
for(auto [l,r]:all[i]){
if(curr_l==-1){
curr_l = l, curr_r = r;
}
else{
if(curr_r+1<l or r+1<curr_l){
bad(n); return 0;
}
curr_l = min(curr_l,l);
curr_r = max(curr_r,r);
}
}
if(curr_l==-1 and curr_r==-1){
continue;
}
add[curr_l].pb(i);
if(curr_r+1<n){
sub[curr_r+1].pb(i);
}
}
priority_queue<int>pq;
pq.push(-1);
for(int i = 0;i<n;i++){
//tmp[i] = seg.query(i,i).sum;
for(auto t : sub[i]){
remove[t] = true;
}
for(auto t : add[i]){
pq.push(t);
}
while(true){
int x = pq.top();
if(x==-1){
break;
}
if(remove[x]){
pq.pop();
}
else{
break;
}
}
tmp[i] = pq.top();
}
vector<int>ans(n,-1);
for(int i = 0;i<n;i++){
if(tmp[i]==-1){
continue;
}
if(fs.count(tmp[i]) and a[tmp[i]].first<=i and i<=a[tmp[i]].second){
ans[i] = tmp[i];
fs.erase(fs.find(tmp[i]));
}
}
if(fs.size()!=0){
bad(n); return 0;
}
// // Put the other numbers
// If there are restrictions
for(int i = 0;i<n;i++){
if(tmp[i]==-1 or ans[i]!=-1){
continue;
}
auto it = lower_bound(others.begin(),others.end(),tmp[i]);
if(n<=1000){
if(it==others.end()){
bad(n); return 0;
}
ans[i] = *it;
others.erase(it);
}
}
if(n<=1000){
// // If no restricitons left
for(int i = 0;i<n;i++){
if(ans[i]==-1){
if(others.size()==0){
bad(n); return 0;
}
auto it = others.begin();
ans[i] = *it;
others.erase(it);
}
}
SegTree seg3(ans);
for(int i = 0;i<n;i++){
for(auto [l,r]:all[i]){
if(seg3.query(l,r).sum!=i){
bad(n); return 0;
}
}
}
for(auto x : ans) cout << x << ' ';
}
}
