#include <bits/stdc++.h>
#include <atcoder/all>
//eolibraries
#define lnf 3999999999999999999
#define inf 999999999+1
#define fi first
#define se second
#define pb push_back
#define all(c) (c).begin(),(c).end()
#define sz(c) (int)(c).size()
#define make_unique(a) sort(all(a)),a.erase(unique(all(a)),a.end());
#define rep(i,n) for(int i=0;i<n;i++)
#define drep(i,n) for(int i=n-1;i>=0;i--)
#define crep(i,x,n) for(int i=x;i<n;i++)
#define vec(...) vector<__VA_ARGS__>
#define _3E0svGb ios_base::sync_with_stdio(false),cin.tie(0),cout.tie(0)
//eodefine
using namespace std;
typedef long long ll;
typedef long double ld;
using pii=pair<int,int>;
using tpii=pair<int,pii>;
using vi=vec(int);
const int mxn=12000;

int op(int l,int r){
	return min(l,r);
}

int e(){
	return inf;
}

int main(){
_3E0svGb;
	int n,m;
	cin>>n>>m;
	vec(tpii) qry;
	rep(i,m){
		ll l,r,val;
		cin>>l>>r>>val;
		l--,r--;
		qry.pb({val,{l,r}});
	}
	sort(all(qry));
	reverse(all(qry));
	vec(ll) a(n,-1);
	set<int> st;
	rep(i,n) st.insert(i);
	atcoder::segtree<int,op,e> seg(n);
	rep(i,n) seg.set(i,inf);
	rep(i,sz(qry)){
		int l=qry[i].se.fi,r=qry[i].se.se;
		int val=qry[i].fi;
		auto it=st.lower_bound(l);
		if((it==st.end() or *it>r) and seg.prod(l,r+1)>val){
			printf("-1\n");
			exit(0);
		}
		while(true){
			auto ti=st.lower_bound(l);
			if(*ti>r or ti==st.end()) break;
			a[*ti]=val;
			seg.set(*ti,val);
			st.erase(ti);
		}
	}
	rep(i,n){
		cout<<(a[i]==-1?inf:a[i]);
		if(i<n-1) cout<<" ";
	}
	cout<<"\n";
//	
	return 0;
}