#include <string>
#include <vector>
#include<iostream>
#include<cstdio>
#include<cstdlib>
#include<stack>
#include<queue>
#include<cmath>
#include<algorithm>
#include<functional>
#include<list>
#include<deque>
#include<bitset>
#include<set>
#include<map>
#include<unordered_map>
#include<unordered_set>
#include<cstring>
#include<sstream>
#include<complex>
#include<iomanip>
#include<numeric>
#include<cassert>
#include<random>
#define X first
#define Y second
#define pb push_back
#define rep(X,Y) for (int (X) = 0;(X) < (int)(Y);++(X))
#define reps(X,S,Y) for (int (X) = (int)(S);(X) < (int)(Y);++(X))
#define rrep(X,Y) for (int (X) = (int)(Y)-1;(X) >=0;--(X))
#define rreps(X,S,Y) for (int (X) = (int)(Y)-1;(X) >= (int)(S);--(X))
#define repe(X,Y) for ((X) = 0;(X) < (Y);++(X))
#define peat(X,Y) for (;(X) < (Y);++(X))
#define all(X) (X).begin(),(X).end()
#define rall(X) (X).rbegin(),(X).rend()
#define eb emplace_back
#define UNIQUE(X) (X).erase(unique(all(X)),(X).end())
#define Endl endl
#define NL <<"\n"
#define cauto const auto

using namespace std;
using ll=long long;
using pii=pair<int,int>;
using pll=pair<ll,ll>;
template<class T> using vv=vector<vector<T>>;
template<class T> inline bool MX(T &l,const T &r){return l<r?l=r,1:0;}
template<class T> inline bool MN(T &l,const T &r){return l>r?l=r,1:0;}
//#undef NUIP
#ifdef NUIP
#include "benri.h"
#else
#define out(args...)
#endif
void ouT(ll x,int d=3){auto re=to_string(x);if((int)re.size()>d) re=x>0?"oo":"-oo";cout<<string(d-re.size(),' ')<<re<<",";}
#ifdef __cpp_init_captures
template<typename T>vector<T> table(int n, T v){ return vector<T>(n, v);}
template <class... Args> auto table(int n, Args... args){auto val = table(args...); return vector<decltype(val)>(n, move(val));}
#endif
template<class A,class B> pair<A,B> operator+(const pair<A,B> &p,const pair<A,B> &q){ return {p.X+q.X,p.Y+q.Y};}
template<class A,class B,class C,class D> pair<A,B>& operator+=(pair<A,B> &p,const pair<C,D> &q){ p.X+=q.X; p.Y+=q.Y; return p;}
template<class A,class B> pair<A,B> operator-(const pair<A,B> &p,const pair<A,B> &q){ return {p.X-q.X,p.Y-q.Y};}
template<class A,class B,class C,class D> pair<A,B>& operator-=(pair<A,B> &p,const pair<C,D> &q){ p.X-=q.X; p.Y-=q.Y; return p;}
template<class A,class B> istream& operator>>(istream &is, pair<A,B> &p){ is>>p.X>>p.Y; return is;}
template<class T=ll> T read(){ T re; cin>>re; return re;}
template<class T=ll> T read(const T &dec){ T re; cin>>re; return re-dec;}
template<class T=ll> vector<T> readV(const int sz){ vector<T> re(sz); for(auto &x:re) x=read<T>(); return re;}
template<class T=ll> vector<T> readV(const int sz, const T &dec){ vector<T> re(sz); for(auto &x:re) x=read<T>(dec); return re;}
vv<int> readG(const int &n,const int &m){ vv<int> g(n); rep(_,m){ cauto a=read<int>(1),b=read<int>(1); g[a].pb(b); g[b].pb(a);} return g;}
vv<int> readG(const int &n){ return readG(n,n-1);}
vv<int> readD(const int &n,const int &m){ vv<int> g(n); rep(_,m){ cauto a=read<int>(1),b=read<int>(1); g[a].pb(b); } return g;}
vv<int> readD(const int &n){ return readD(n,n-1);}
template<class T> vv<pair<int,T>> readG(const int &n,const int &m){ vv<pair<int,T>> g(n); rep(_,m){ cauto a=read<int>(1),b=read<int>(1); cauto c=read<T>(); g[a].eb(b,c); g[b].eb(a,c);} return g;}
template<class T> vv<pair<int,T>> readG(const int &n){ return readG<T>(n,n-1);}
template<class T> vv<pair<int,T>> readD(const int &n,const int &m){ vv<pair<int,T>> g(n); rep(_,m){ cauto a=read<int>(1),b=read<int>(1); cauto c=read<T>(); g[a].eb(b,c); } return g;}
template<class T> vv<pair<int,T>> readD(const int &n){ return readD<T>(n,n-1);}
template<class T> bool erase(multiset<T> &st, const T &v){if(cauto it=st.find(v); it==st.end()) return false; else{ st.erase(it); return true;}}
#ifdef __cpp_init_captures
template<typename T> vector<T> readT(int n, T v){ return readV(n,v);}
template <class... Args> auto readT(int n, Args... args){ vector re(1,readT(args...));rep(_,n-1) re.eb(readT(args...));	return re;}
template<typename T, size_t... Is> void addadd(T& t1, const T& t2, integer_sequence<size_t, Is...>){ cauto l = { (get<Is>(t1) += get<Is>(t2), 0)... }; (void)l;}
template <typename...T>tuple<T...>& operator += (tuple<T...>& lhs, const tuple<T...>& rhs){	addadd(lhs, rhs, index_sequence_for<T...>{});	return lhs;}
template <typename...T>tuple<T...> operator +(tuple<T...> lhs, const tuple<T...>& rhs){ return lhs += rhs;}
template<typename T, size_t... Is> void subsub(T& t1, const T& t2, integer_sequence<size_t, Is...>){ cauto l = { (get<Is>(t1) -= get<Is>(t2), 0)... }; (void)l;}
template <typename...T>tuple<T...>& operator -= (tuple<T...>& lhs, const tuple<T...>& rhs){	subsub(lhs, rhs, index_sequence_for<T...>{});	return lhs;}
template <typename...T>tuple<T...> operator - (tuple<T...> lhs, const tuple<T...>& rhs){ return lhs -= rhs;}
template<class Tuple, size_t... Is> void read_tuple_impl(istream &is, Tuple& t, index_sequence<Is...>){((is >> get<Is>(t)), ...);}
template<class... Args> auto& operator>>(istream &is, tuple<Args...>& t){ read_tuple_impl(is, t, index_sequence_for<Args...>{}); return is;}
#endif
#define TT cauto TTT=read();rep(_,TTT)
const ll MOD=1e9+7; //998244353;

struct Seg{
	int mx;
  Seg(int d=-MOD):mx(d){}
  static Seg e;
};
Seg Seg::e=Seg();

Seg operator+(const Seg &l,const Seg &r){
  return max(l.mx,r.mx);
}

template<class Seg>
struct CoSegTree{
	vector<Seg> segs;
	void add(int k,Seg a){
		k+=segs.size()/2-1;
		segs[k]=segs[k]+a;
		upd(k);
	}
	void assign(int k,Seg a){
		k+=segs.size()/2-1;
		segs[k]=a;
		upd(k);
	}
	void upd(int k){
		while(k>0){
			k=(k-1)/2;
			segs[k]=segs[k*2+1]+segs[k*2+2];
		}
	}
	void upd(){	rrep(k,segs.size()/2-1) segs[k]=segs[k*2+1]+segs[k*2+2];}
	
	//(l,r,0,0,nn)
	void upd(int a,int b,const Seg &seg){
		upd(a,b,seg,0,0,segs.size()/2);
	}
	void upd(int a,int b,const Seg &seg,int k,int l,int r){
		if(r<=a || b<=l) return;
		if(a<=l && r<=b){
			out(l,r,1);
			segs[k]=segs[k]+seg;
			return;
		}
		upd(a,b,seg,k*2+1,l,(l+r)/2);
		upd(a,b,seg,k*2+2,(l+r)/2,r);
	}
	Seg query(int x){
		x+=segs.size()/2-1;
		auto re=segs[x];
		while(x>0){
			x=(x-1)/2;
			re=re+segs[x];
		}
		return re;
	}

	CoSegTree(int n){
		int pw=1;
		while(pw<n) pw*=2;
		segs.resize(2*pw);
	}
	void operator()(int l,int r,const Seg &seg){ upd(max(0,l),min((int)segs.size()/2,r),seg);}
	Seg operator[](const int &i){ return query(i);}
	Seg rb(int r){ return operator()(0,r); }
	Seg lb(int l){ return operator()(l,segs.size()/2); }
};

template<class SegTree>
struct SegTreeUpdater{
	SegTree *st;
	int i;
	SegTreeUpdater(SegTree *st,int i):st(st),i(i){}
	template<class Seg> void operator+=(const Seg &seg){ st->add(i,seg);}
	template<class Seg> void operator=(const Seg &seg){	st->assign(i,seg);}
};

template<class Seg>
struct SegTree{
	vector<Seg> segs;
	void add(int k,Seg a){
		k+=segs.size()/2-1;
		segs[k]=segs[k]+a;
		upd(k);
	}
	void assign(int k,Seg a){
		k+=segs.size()/2-1;
		segs[k]=a;
		upd(k);
	}
	void upd(int k){
		while(k>0){
			k=(k-1)/2;
			segs[k]=segs[k*2+1]+segs[k*2+2];
		}
	}
	void upd(){	rrep(k,segs.size()/2-1) segs[k]=segs[k*2+1]+segs[k*2+2];}
	
	//(l,r,0,0,nn)
	template<class T=Seg> T query(int a,int b,int k,int l,int r){
		if(r<=a || b<=l)return T::e;
		if(a<=l && r<=b) return segs[k];
		T lv=query(a,b,k*2+1,l,(l+r)/2) ,rv= query(a,b,k*2+2,(l+r)/2,r);
		return lv+rv;
	}

	SegTree(int n){
		int pw=1;
		while(pw<n) pw*=2;
		segs.resize(2*pw);
	}
	SegTreeUpdater<SegTree<Seg>> operator[](int i){ return {this,i};}
	Seg operator()(int l,int r){ return query(max(0,l),min((int)segs.size()/2,r),0,0,segs.size()/2);};
	Seg& operator()(int i){ return segs[segs.size()/2-1+i];}
	Seg operator()(){ return segs[0];}
	Seg rb(int r){ return operator()(0,r); }
	Seg lb(int l){ return operator()(l,segs.size()/2); }
};

int main(){
	ios_base::sync_with_stdio(false); cin.tie(0);
	cout<<fixed<<setprecision(0);
	cauto n=read();
	cauto q=read();
	cauto ts=readV<tuple<int,int,int>>(q,{1,0,0});
	vector<int> re(n);
	{
		CoSegTree<Seg> st(n);
		st(0,n,1-000000000);
		for(cauto &[l,r,x]:ts) st(l,r,x);
		rep(i,n) re[i]=st[i].mx;
	}
	out(re,1);
	SegTree<Seg> st(n);
	rep(i,n) st[i]=-re[i];
	for(cauto &[l,r,x]:ts){
		if(st(l,r).mx==-x) continue;
		cout<<-1 NL;
		exit(0);
	}
	rep(i,n) cout<<re[i]<<" \n"[i+1==n];
	return 0;
}