#include<iostream>
#include<vector>
#include<algorithm>
#include<queue>
#include<atcoder/segtree>
using namespace std;
int op(int a,int b){return a<b?a:b;}
int e(){return 2e9;}
int N,Q;
vector<pair<int,int> >L[2<<17];
main()
{
	cin>>N>>Q;
	for(int i=0;i<Q;i++)
	{
		int l,r,b;cin>>l>>r>>b;
		L[l-1].push_back(make_pair(b,r));
	}
	priority_queue<pair<int,int> >P;
	vector<int>A(N);
	P.push(make_pair(1,N));
	for(int l=0;l<N;l++)
	{
		while(P.top().second<=l)P.pop();
		for(pair<int,int>p:L[l])P.push(p);
		A[l]=P.top().first;
	}
	atcoder::segtree<int,op,e>Q(A);
	for(int l=0;l<N;l++)
	{
		for(pair<int,int>p:L[l])
		{
			int r=p.second,b=p.first;
			if(Q.prod(l,r)!=b)
			{
				cout<<-1<<endl;
				return 0;
			}
		}
	}
	for(int i=0;i<N;i++)cout<<A[i]<<(i+1==N?"\n":" ");
}