#include <bits/stdc++.h>
#define f first
#define s second
using namespace std;
const int MAXN = 1e5+11;
struct segtree{
int T[MAXN<<2];
void init(){
fill(T,T+(MAXN<<2),-1);
}
void update(int findl, int findr, int val, int l, int r, int cur){
if(findr < l || r < findl) return;
if(findl <= l && r <= findr){
T[cur] = max(T[cur],val);
return;
}
T[2*cur+1] = max(T[cur],T[2*cur+1]);
T[2*cur+2] = max(T[cur],T[2*cur+2]);
int m = (l+r)/2;
update(findl,findr,val,l,m,2*cur+1);
update(findl,findr,val,m+1,r,2*cur+2);
T[cur] = min(T[2*cur+1],T[2*cur+2]);
}
int query(int findl, int findr, int l, int r, int cur){
if(findr < l || r < findl) return (1<<30);
if(findl <= l && r <= findr) return T[cur];
T[2*cur+1] = max(T[cur],T[2*cur+1]);
T[2*cur+2] = max(T[cur],T[2*cur+2]);
int m = (l+r)/2;
return min(query(findl,findr,l,m,cur*2+1),query(findl,findr,m+1,r,cur*2+2));
}
}seg1,seg2;
struct rmq{
int l,r,x;
};
bool cmp(rmq a, rmq b){
return a.r-a.l < b.r-b.l;
}
vector<rmq> qs[MAXN];
int LL[MAXN], RR[MAXN], L[MAXN], R[MAXN], ans[MAXN];
bool used[MAXN], used2[MAXN];
int main()
{
int N,Q; cin >> N >> Q;
vector<rmq> queries;
for(int i = 0;i<Q;++i){
int l,r,x; cin >> l >> r >> x;
queries.push_back({l,r,x});
qs[x].push_back({l,r,x});
seg1.update(l,r,x,0,N-1,0);
}
auto ret = [&N](){
for(int i = 0;i<N;++i) cout << -1 << " ";
cout << "\n";
exit(0);
};
for(int i = 0;i<Q;++i){
int c = seg1.query(queries[i].l,queries[i].r,0,N-1,0);
if(c != queries[i].x) ret();
}
for(int i = 0;i<N;++i){
int curl = 0, curr = N-1;
for(int j = 0;j<qs[i].size();++j){
curl = max(curl,qs[i][j].l);
curr = min(curr,qs[i][j].r);
//cout << i << " " << qs[i][j].l << " " << qs[i][j].r << "\n";
}
if(curl > curr) ret();
LL[i] = curl; RR[i] = curr;
}
for(int i = 0;i<N;++i){
L[i] = 1<<30; R[i] = -1<<30;
}
for(int i = 0;i<N;++i){
int c = seg1.query(i,i,0,N-1,0);
if(c == -1) continue;
if(LL[c] <= i && i <= RR[c]){
L[c] = min(L[c],i);
R[c] = max(R[c],i);
}
}
vector<rmq> nxt;
for(int i = 0;i<N;++i){
if(qs[i].size()){
if(L[i] > R[i]){
ret();
}
nxt.push_back({L[i],R[i],i});
}
}
sort(nxt.begin(),nxt.end(),cmp);
auto sign = [](int i, int val){
used[i] = true, used2[val] = true;
ans[i] = val;
};
for(auto s : nxt){
for(int j = s.l;j <= s.r;++j){
if(!used[j]){
sign(j,s.x);
break;
}
}
}
priority_queue<pair<int,int>,vector<pair<int,int>>,greater<pair<int,int>>> pq;
for(int i = 0;i<N;++i){
if(!used[i]){
int c = seg1.query(i,i,0,N-1,0);
pq.push({c,i});
}
}
for(int i = 0;i<N;++i){
if(!used2[i]){
int se = pq.top().s; pq.pop();
ans[se] = i;
}
}
for(int i = 0;i<N;++i) seg2.update(i,i,ans[i],0,N-1,0);
//for(int i = 0;i<N;++i) cout << ans[i] << " ";
//cout << "\n";
for(int i = 0;i<Q;++i){
int c = seg2.query(queries[i].l,queries[i].r,0,N-1,0);
//cout << c << "\n";
if(c != queries[i].x) ret();
}
for(int i = 0;i<N;++i){
cout << ans[i] << " ";
}
cout << "\n";
return 0;
}
