//
//                               S i r o t a n   w a t c h e s   o v e r   y o u .
//
//                                          ...Jggg+J+JJJg@NQmgJa.....,       
//                                 ....gH@@@@HHB""""7"YYYYHMMMMMMM@@@@@@@Hma,.   
//                            ...JH@@MMHY"!                        ? __""YH@@@@N&...     
//                        ..JH@@HY"~                                          _TW@@@Mme.    
//                     .Jg@@#"=                                                   _TTM@@N..     
//                  .Jg@@MY!                                                          ?T@@@h,.   
//                .-@@@B!                                                                (TM@@@L     
//              .(H@MY                                                                      ?W@@@+    
//             .W@@@                                                                          .T@@@[       
//           .d@@M!                                                                             .T@@N,   
//          .d@M@'                                                                                -W@@o. 
//         (@@M\                                                                                    ?M@N,
//        -d@M%                    ..,                                      ..,                      j@@b  
//       d@@M=                     TM9                                      ?MD                       W@@[ 
//      .H@M:                                                                                         .W@H,
//      H@Ht                                                                                           ,@@#   
//     (@@M~                                                                                           .@@h.
//    .@@M%                        ..gmHHJ.                             .JdHga.                        .H@@e  
//    j@@#_                       .@@@@@@@b                            J@@@@@@@h.                      .H@@\ 
//    d@@@                       .4@@@@@@MF                            (@@@@@@@@                        H@@b  
//    d@@[                         ?"BMY"=            .d@@@@H,          ?TWHHY"!                        d@@e    
//    J@@b          .JJJ-..,                         ,@@@@@@M%                       .........         -@@@M. 
//    ?@@M\         ?YHHM@@@@b                ..      .W@@HP                        X@@HMWY"=          d@@@#
//    ,@@@L.                                 ?H@Ng&+gd@@#H@@NHaJ+gH@[                                  J@@@] 
//     X@@@[            ......                 ?"YYYYY""   ?"YHHHB"^                 .....            (@@@#   
//      WH@N+.      .W@@@@MHB=                                                      .TWH@M@Hmc       .H@@M~    
//     .H@@@@N,      _!~                                                                            .d@@@N,   
//   .J@@#T@@@N,                                                                                  .d@@@@@@@b. 
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// (@@@F      4@@@@MaJ.                                                                       .d@@@@Y77   4@@@r 
//.H@@P         ?TM@@@@N...                                                               .-JH@HMY=        d@@N,
//(@@@F             ?"WM@@@MQa-,.                                                  .(J(JN@@M#"             Z@@@L
// d@@H,                 (M@@@@@@@Ng&maJ....                           .. ...J.J+W@@@@@@HY!               .dH@b 
// ?M@@@N&.        ..(JW@@@MM"?7""TYHMH@@HH@@@@@HHHgkHagHa(mggdmmagH@H@@Q@@HMMMHY"7!TMM@@@HaJ,.        ..H@@@M^ 
//   ?"W@@@@MN@@@@@H@@MMY"                  _???!"= ?WMMBYYTMH=7""Y@""?"~^             _"YM@@@@@@@@MH@@@@@#"^ 
//       ?77WMMMYB""!                                                                        _7"WWMMMY"7=     

// need
#include <iostream>
#include <algorithm>
// data structure
#include <bitset>
#include <map>
#include <queue>
#include <set>
#include <stack>
#include <string>
#include <cstring>
#include <utility>
#include <vector>
#include <complex>
//#include <deque>
#include <valarray>
#include <unordered_map>
#include <unordered_set>
#include <array>
// etc
#include <cassert>
#include <cmath>
#include <functional>
#include <iomanip>
#include <chrono>
#include <random>
#include <numeric>
#include <fstream>

//std::ifstream ifs("d.in");
//auto& scan_in = ifs;
auto& scan_in = std::cin;
auto& scan_out = std::cout;

// input
#define INIT std::ios::sync_with_stdio(false);std::cin.tie(0);
#define VAR(type, ...)type __VA_ARGS__;MACRO_VAR_Scan(__VA_ARGS__);
template<typename T> void MACRO_VAR_Scan(T& t) { scan_in >> t; }
template<typename First, typename...Rest>void MACRO_VAR_Scan(First& first, Rest& ...rest) { scan_in >> first; MACRO_VAR_Scan(rest...); }
#define VEC_ROW(type, n, ...)std::vector<type> __VA_ARGS__;MACRO_VEC_ROW_Init(n, __VA_ARGS__); for(int w_=0; w_<n; ++w_){MACRO_VEC_ROW_Scan(w_, __VA_ARGS__);}
template<typename T> void MACRO_VEC_ROW_Init(int n, T& t) { t.resize(n); }
template<typename First, typename...Rest>void MACRO_VEC_ROW_Init(int n, First& first, Rest& ...rest) { first.resize(n); MACRO_VEC_ROW_Init(n, rest...); }
template<typename T> void MACRO_VEC_ROW_Scan(int p, T& t) { scan_in >> t[p]; }
template<typename First, typename...Rest>void MACRO_VEC_ROW_Scan(int p, First& first, Rest& ...rest) { scan_in >> first[p]; MACRO_VEC_ROW_Scan(p, rest...); }
#define VEC(type, c, n) std::vector<type> c(n);for(auto& i:c)scan_in>>i;
#define MAT(type, c, m, n) std::vector<std::vector<type>> c(m, std::vector<type>(n));for(auto& R:c)for(auto& w:R)scan_in>>w;
// output
template<typename T>void MACRO_OUT(const T t) { scan_out << t; }
template<typename First, typename...Rest>void MACRO_OUT(const First first, const Rest...rest) { scan_out << first << ' '; MACRO_OUT(rest...); }
#define OUT(...) MACRO_OUT(__VA_ARGS__);
#define FOUT(n, dist) scan_out<<std::fixed<<std::setprecision(n)<<(dist);
#define SOUT(n, c, dist) scan_out<<std::setw(n)<<std::setfill(c)<<(dist);
#define VOUT(v) for(size_t i = 0; i < v.size(); ++i) {OUT(v[i]);if(i+1<v.size()){SP}}
#define EOUT(...) do{ OUT(__VA_ARGS__)BR; exit(0); }while(0);
#define SP scan_out<<' ';
#define TAB scan_out<<'\t';
#define BR scan_out<<'\n';
#define SPBR(w, n) scan_out<<(w + 1 == n ? '\n' : ' ');
#define ENDL scan_out<<std::endl;
#define FLUSH scan_out<<std::flush;
#define SHOW(dist) {std::cerr << #dist << "\t: " << (dist) << '\n';}
// utility
#define ALL(a) (a).begin(),(a).end()
#define FOR(w, a, n) for(int w=(a);w<(n);++w)
#define REP(w, n) FOR(w, 0, n)
#define RFOR(w, a, n) for(int w=(n)-1;w>=(a);--w)
#define RREP(w, n) RFOR(w, 0, n)
template<class S, class T, class U> bool IN(S a, T x, U b) { return a <= x && x < b; }
template<class T> inline bool CHMAX(T& a, const T b) { if (a < b) { a = b; return true; } return false; }
template<class T> inline bool CHMIN(T& a, const T b) { if (a > b) { a = b; return true; } return false; }
// test
template<class T> using V = std::vector<T>;
template<class T> using VV = V<V<T>>;
//
//std::ostream& operator<<(std::ostream& os, const __int128& t) {
//	if (t >= 1000000000000000000) {
//		os << (long long)(t / 1000000000000000000) << (long long)(t % 1000000000000000000);
//	}
//	else {
//		os << (long long)t;
//	}
//	return os;
//}
template<typename S, typename T>
std::ostream& operator<<(std::ostream& os, const std::pair<S, T>& p) {
	os << '(' << p.first << ',' << p.second << ')';
	return os;
}
template<typename T>
std::ostream& operator<<(std::ostream& os, const std::vector<T>& v) {
	os << '{';
	for (size_t i = 0; i < v.size(); ++i) os << v[i] << ((i + 1 < v.size()) ? ',' : '}');
	return os;
}
template<typename T>
std::ostream& operator<<(std::ostream& os, const std::set<T>& v) {
	os << '{';
	for (auto it = v.cbegin(); it != v.cend();) {
		os << *it << (++it == v.cend() ? '}' : ',');
	}
	return os;
}
template<typename S, typename T>
std::ostream& operator<<(std::ostream& os, const std::map<S, T>& m) {
	os << '{';
	for (auto it = m.cbegin(); it != m.cend();) { os << it->first << ':' << it->second; ++it; os << (it != m.cend() ? ',' : '}'); }
	return os;
}
template<typename T>
std::ostream& operator<<(std::ostream& os, std::queue<T> q) {
	os << '<';
	while (!q.empty()) { os << q.front(); q.pop(); os << (q.empty() ? '<' : ','); }
	return os;
}
template<typename T>
std::ostream& operator<<(std::ostream& os, std::stack<T> q) {
	os << '>';
	while (!q.empty()) { os << q.top(); q.pop(); os << (q.empty() ? ']' : ','); }
	return os;
}
namespace std {
	template<typename S, typename T> class numeric_limits<pair<S, T>> {
	public:
		static constexpr pair<S, T> max() noexcept { return { numeric_limits<S>::max(), numeric_limits<T>::max() }; }
		static constexpr pair<S, T> lowest() noexcept { return { numeric_limits<S>::lowest(), numeric_limits<T>::lowest() }; }
	};
}

// type/const
using i64 = long long;
using u64 = unsigned long long;
using ll = long long;
using ull = unsigned long long;
using ld = long double;
using PAIR = std::pair<int, int>;
constexpr int INFINT = (1 << 30) - 1;                    // 1.07x10^ 9
constexpr int INFINT_LIM = (1LL << 31) - 1;              // 2.15x10^ 9
constexpr long long INFLL = 1LL << 60;                          // 1.15x10^18
constexpr long long INFLL_LIM = (1LL << 62) - 1 + (1LL << 62);  // 9.22x10^18
constexpr double EPS = 1e-12;
constexpr int MOD = 998244353;
constexpr double PI = 3.141592653589793238462643383279;
template<class T, size_t N> void FILL(T(&a)[N], const T& val) { for (auto& x : a) x = val; }
template<class ARY, size_t N, size_t M, class T> void FILL(ARY(&a)[N][M], const T& val) { for (auto& b : a) FILL(b, val); }
template<class T> void FILL(std::vector<T>& a, const T& val) { for (auto& x : a) x = val; }
template<class ARY, class T> void FILL(std::vector<std::vector<ARY>>& a, const T& val) { for (auto& b : a) FILL(b, val); }
// ------------>8------------------------>8------------

// ------------>8------------ SegmentTree ------------>8------------

namespace Monoid {
	template <class T> class sum {
	public:
		using value_type = T;
		inline static T operation(const T& a, const T& b) { return a + b; }
		inline static T identity() { return T(0); }
	};
	template <class T> class max {
	public:
		using value_type = T;
		inline static T operation(const T& a, const T& b) { return (a < b) ? b : a; }
		inline static T identity() { return std::numeric_limits<T>::lowest(); }
	};
	template <class T> class min {
	public:
		using value_type = T;
		inline static T operation(const T& a, const T& b) { return (a < b) ? a : b; }
		inline static T identity() { return std::numeric_limits<T>::max(); }
	};

	class MONOID {
	public:
		struct S { int x; };
		using value_type = S;
		inline static S operation(const S& l, const S& r) { return S{ l.x + r.x }; }
		inline static S identity() { return S{ 0 }; }
	};
}
template <class Monoid>
class SegmentTree {
private:
	using T = typename Monoid::value_type;
	int ARY_SIZE;
	std::vector<T> ary;

	void init(int n) {
		while (ARY_SIZE < n) ARY_SIZE <<= 1;
		ary.resize(ARY_SIZE << 1, Monoid::identity());
	}
public:
	SegmentTree(int n) : ARY_SIZE(1) { init(n); }
	SegmentTree(std::vector<T>& a) : ARY_SIZE(1) {
		init(a.size());
		std::copy(a.begin(), a.end(), ary.begin() + ARY_SIZE);
		for (int i = ARY_SIZE - 1; i >= 1; --i) {
			ary[i] = Monoid::operation(ary[i << 1], ary[(i << 1) + 1]);
		}
	}

	// -- a[i] = val;
	inline void update(int i, T val) {
		i += ARY_SIZE;
		ary[i] = val;
		while (i > 1) {
			i >>= 1;
			ary[i] = Monoid::operation(ary[i << 1], ary[(i << 1) + 1]);
		}
	}
	// -- a[i] += val;
	inline void add(int i, T val) {
		update(i, ary[i + ARY_SIZE] + val);
	}
	// -- [l, r)
	inline T query(int l, int r) {
		if (l >= r) return Monoid::identity();
		T vl = Monoid::identity(), vr = Monoid::identity();
		for (l += ARY_SIZE, r += ARY_SIZE; l != r; l >>= 1, r >>= 1) {
			if (l & 1) vl = Monoid::operation(vl, ary[l++]);
			if (r & 1) vr = Monoid::operation(ary[--r], vr);
		}
		return Monoid::operation(vl, vr);
	}
	T operator[](int i) { return ary[i + ARY_SIZE]; }

	void debugShow() {
		for (int i = ARY_SIZE; i < ARY_SIZE << 1; ++i) std::cerr << ary[i] << " ";
		std::cerr << "\n";
	}
};
// ------------8<------------ SegmentTree ------------8<------------

// Description: 区間をsetで管理するデータ構造(なお実装はmap)．各クエリO(log区間数)．

// #### attention! : [l, r] ( include r, not [l, r) )
class SegmentMap : public std::map<signed, signed> {
private:
	bool flagToMergeAdjacentSegment;
public:
	// if merge [l, c] and [c+1, r], set flagToMergeAdjacentSegment to true
	SegmentMap(bool flagToMergeAdjacentSegment) :
		flagToMergeAdjacentSegment(flagToMergeAdjacentSegment) {}
	// __exist -> iterator pair(l, r) (contain p)
	// noexist -> map.end()
	auto get(signed p) const {
		auto it = upper_bound(p);
		if (it == begin() || (--it)->second < p) return end();
		return it;
	}
	// insert segment [l, r]
	void insert(signed l, signed r) {
		auto itl = upper_bound(l), itr = upper_bound(r + flagToMergeAdjacentSegment);
		if (itl != begin()) {
			if ((--itl)->second < l - flagToMergeAdjacentSegment) ++itl;
		}
		if (itl != itr) {
			l = std::min(l, itl->first);
			r = std::max(r, std::prev(itr)->second);
			erase(itl, itr);
		}
		(*this)[l] = r;
	}
	// remove segment [l, r]
	void remove(signed l, signed r) {
		auto itl = upper_bound(l), itr = upper_bound(r);
		if (itl != begin()) {
			if ((--itl)->second < l) ++itl;
		}
		if (itl == itr) return;
		int tl = std::min(l, itl->first), tr = std::max(r, std::prev(itr)->second);
		erase(itl, itr);
		if (tl < l) (*this)[tl] = l - 1;
		if (r < tr) (*this)[r + 1] = tr;
	}
	// Is p and q in same segment?
	bool same(signed p, signed q) const {
		const auto&& it = get(p);
		return it != end() && it->first <= q && q <= it->second;
	}
};

signed main() {
	INIT;

	VAR(int, n, q);
	VEC_ROW(int, q, l, r, b);

	SegmentMap sm(true);
	SegmentTree<Monoid::min<int>> st(n);
	REP(i, n) st.update(i, 1000000000);
	{
		VV<int> d(q);
		REP(i, q) d[i] = { --l[i], --r[i], b[i], i };
		std::sort(ALL(d), [&](V<int>& tl, V<int>& tr) {
			if (tl[2] == tr[2]) return tl[3] < tr[3];
			return tl[2] > tr[2];
			});
		REP(i, q) {
			l[i] = d[i][0];
			r[i] = d[i][1];
			b[i] = d[i][2];
		}
	}
	REP(i, q) {
		if (st.query(l[i], r[i] + 1) == b[i]) continue;

		auto it = sm.get(l[i]);
		if (it == sm.end()) {
			st.update(l[i], b[i]);
		}
		else {
			if (it->second < r[i]) {
				st.update(it->second + 1, b[i]);
			}
		}
		sm.insert(l[i], r[i]);
	}

	REP(i, q) {
		if (st.query(l[i], r[i] + 1) != b[i]) { EOUT(-1); }
	}
	REP(i, n) {
		OUT(st.query(i, i + 1))SPBR(i, n);
	}

	return 0;
}