import sys
from collections import defaultdict, Counter, deque
from itertools import permutations, combinations, product, combinations_with_replacement, groupby, accumulate
import operator
from math import sqrt, gcd, factorial
#from math import isqrt, prod, comb  #python3.8用(notpypy)
#from bisect import bisect_left, bisect_right
#from functools import lru_cache, reduce
#from heapq import heappush, heappop, heapify, heappushpop, heapreplace
#import numpy as np
#import networkx as nx
#from networkx.utils import UnionFind
#from numba import njit, b1, i1, i4, i8, f8
#numba例 @njit(i1(i4[:], i8[:, :]),cache=True) 引数i4配列、i8 2次元配列,戻り値i1
#from scipy.sparse import csr_matrix
#from scipy.sparse.csgraph import shortest_path, floyd_warshall, dijkstra, bellman_ford, johnson, NegativeCycleError, maximum_bipartite_matching, maximum_flow, minimum_spanning_tree
def input(): return sys.stdin.readline().rstrip()
def divceil(n, k): return 1+(n-1)//k  # n/kの切り上げを返す
def yn(hantei, yes='Yes', no='No'): print(yes if hantei else no)

#ライブラリ参照https://atcoder.jp/contests/practice2/submissions/20978786
class LazySegmentTree2:
 
    __slots__ = ["n", "data", "lazy", "me", "oe", "fmm", "fmo", "foo"]
 
    def __init__(self, monoid_data, monoid_identity, operator_identity, func_monoid_monoid, func_monoid_operator, func_operator_operator):
        self.me = monoid_identity
        self.oe = operator_identity
        self.fmm = func_monoid_monoid
        self.fmo = func_monoid_operator
        self.foo = func_operator_operator
 
        self.n = len(monoid_data)
        self.data = monoid_data * 2
        for i in range(self.n-1, 0, -1):
            self.data[i] = self.fmm(self.data[2*i], self.data[2*i+1])
        self.lazy = [self.oe] * (self.n * 2)
        
 
    def replace(self, index, value):
        index += self.n
 
        # propagation
        for shift in range(index.bit_length()-1, 0, -1):
            i = index >> shift
            self.lazy[2*i]   = self.foo(self.lazy[2*i],   self.lazy[i])
            self.lazy[2*i+1] = self.foo(self.lazy[2*i+1], self.lazy[i])
            self.data[i] = self.fmo(self.data[i], self.lazy[i])
            self.lazy[i] = self.oe
 
        # update
        self.data[index] = value
        self.lazy[index] = self.oe
 
        # recalculation
        i = index
        while i > 1:
            i //= 2
            self.data[i] = self.fmm( self.fmo(self.data[2*i], self.lazy[2*i]), self.fmo(self.data[2*i+1], self.lazy[2*i+1]) )
            self.lazy[i] = self.oe
 
 
    def effect(self, l, r, operator):
        l += self.n
        r += self.n
        
        # preparing indices
        indices = []
        l0 = (l // (l & -l))     // 2
        r0 = (r // (r & -r) - 1) // 2
        while r0 > l0:
            indices.append(r0)
            r0 //= 2
        while l0 > r0:
            indices.append(l0)
            l0 //= 2
        while l0 and l0 != r0:
            indices.append(r0)
            r0 //= 2
            if l0 == r0:
                break
            indices.append(l0)
            l0 //= 2
        while r0:
            indices.append(r0)
            r0 //= 2
 
        # propagation
        for i in reversed(indices):
            self.lazy[2*i]   = self.foo(self.lazy[2*i],   self.lazy[i])
            self.lazy[2*i+1] = self.foo(self.lazy[2*i+1], self.lazy[i])
            self.data[i] = self.fmo(self.data[i], self.lazy[i])
            self.lazy[i] = self.oe
 
        # effect
        while l < r:
            if l % 2:
                self.lazy[l] = self.foo(self.lazy[l], operator)
                l += 1
            if r % 2:
                r -= 1
                self.lazy[r] = self.foo(self.lazy[r], operator)
            l //= 2
            r //= 2
 
        # recalculation
        for i in indices:
            self.data[i] = self.fmm( self.fmo(self.data[2*i], self.lazy[2*i]), self.fmo(self.data[2*i+1], self.lazy[2*i+1]) )
            self.lazy[i] = self.oe
            
        
    def folded(self, l, r):
        l += self.n
        r += self.n
 
        # preparing indices
        indices = []
        l0 = (l // (l & -l))     // 2
        r0 = (r // (r & -r) - 1) // 2
        while r0 > l0:
            indices.append(r0)
            r0 //= 2
        while l0 > r0:
            indices.append(l0)
            l0 //= 2
        while l0 and l0 != r0:
            indices.append(r0)
            r0 //= 2
            if l0 == r0:
                break
            indices.append(l0)
            l0 //= 2
        while r0:
            indices.append(r0)
            r0 //= 2
        
        # propagation
        for i in reversed(indices):
            self.lazy[2*i]   = self.foo(self.lazy[2*i],   self.lazy[i])
            self.lazy[2*i+1] = self.foo(self.lazy[2*i+1], self.lazy[i])
            self.data[i] = self.fmo(self.data[i], self.lazy[i])
            self.lazy[i] = self.oe
 
        # fold
        left_folded = self.me
        right_folded = self.me
        while l < r:
            if l % 2:
                left_folded = self.fmm(left_folded, self.fmo(self.data[l], self.lazy[l]))
                l += 1
            if r % 2:
                r -= 1
                right_folded = self.fmm(self.fmo(self.data[r], self.lazy[r]), right_folded)
            l //= 2
            r //= 2
        return self.fmm(left_folded, right_folded)

def main():
    mod = 10**9+7
    mod2 = 998244353
    n,q=map(int, input().split())
    lrb=[list(map(int, input().split())) for i in range(q)]
    lrb.sort(key=lambda x:x[2])
    seg=LazySegmentTree2([10**10]*n,10**10,-1,min,lambda x,y: x if y==-1 else y,lambda x,y: x if y==-1 else y)
    for l,r,b in lrb:
        seg.effect(l-1,r,b)
    for l,r,b in lrb:
        if seg.folded(l-1,r)!=b:
            print(-1)
            return
    print(*[seg.folded(i,i+1) for i in range(n)])



if __name__ == '__main__':
    main()