import sys
import math
sys.setrecursionlimit(10**7)
class lazysegki():
    DEFAULT = {
        'min': 1 << 60,
        'max': -(1 << 60),
    }

    FUNC = {
        'min': min,
        'max': max,
    }
    def __init__(self,N,ls,mode='min'): #葉の数N,要素ls
        self.default = self.DEFAULT[mode]
        self.func = self.FUNC[mode]
        self.N = N
        self.K = (N-1).bit_length()
        self.N0 = 1 << self.K 
        self.dat = [self.default]*(2**(self.K+1)) #全体の配列を用意(maxなら-inf,minなら+infで未構築を表現)　
        self.lazy = [None]*(2**(self.K+1)) #遅延評価
        for i in range(self.N): #葉の構築
            self.dat[2**self.K+i] = ls[i]
        self.build()

    def build(self):
        for j in range(self.N0-1,0,-1):
            self.dat[j] = self.func(self.dat[j<<1],self.dat[j<<1|1]) #親が持つ条件

    def leafvalue(self,x): #x番目の値を出力
        return self.query(x,x+1)

    def gindex(self,l, r): #伝播するインデックス列挙
        L = l + self.N0; R = r + self.N0
        lm = (L // (L & -L)) >> 1
        rm = (R // (R & -R)) >> 1
        lsindex = []
        while L < R:
            if R <= rm:
                lsindex.append(R)
            if L <= lm:
                lsindex.append(L)
            L >>= 1; R >>= 1
        while L:
            lsindex.append(L)
            L >>= 1
        return lsindex

    def propagates(self,ids):
        for i in reversed(ids):
            v = self.lazy[i]
            if v is None:
                continue
            self.lazy[i<<1] = self.dat[i<<1] = self.lazy[i<<1|1] = self.dat[i<<1|1] = v
            self.lazy[i] = None

    def update_replace(self,l, r, x):
        ids = self.gindex(l, r)
        # 1. トップダウンにlazyの値を伝搬
        self.propagates(ids)
    
        # 2. 区間[l, r)のdata, lazyの値を更新
        L = self.N0 + l; R = self.N0 + r
        while L < R:
            if R & 1:
                R -= 1
                self.lazy[R] = self.dat[R] = x
            if L & 1:
                self.lazy[L] = self.dat[L] = x
                L += 1
            L >>= 1; R >>= 1

        # 3. 伝搬させた区間について、ボトムアップにself.dataの値を伝搬する
        #print(ids)
        for i in ids:
            self.dat[i] = self.func(self.dat[i<<1],self.dat[i<<1|1])

    def query(self,l, r):
        self.propagates(self.gindex(l, r))
        L = self.N0 + l
        R = self.N0 + r
        vL = self.default
        vR = self.default
        while L < R:
            if L & 1:
                vL = self.func(vL,self.dat[L])
                L += 1
            if R & 1:
                R -= 1
                vR = self.func(self.dat[R],vR)
            L >>= 1
            R >>= 1
        return self.func(vL,vR)

N,Q = map(int,input().split())
lsQ = []
for i in range(Q):
    l,r,B = map(int,input().split())
    lsQ.append((B,l-1,r))
lsQ.sort()
ll = [10**9]*(N)
LSG = lazysegki(N, ll)
for B,l,r in lsQ:
    LSG.update_replace(l, r, B)

for B,l,r in lsQ:
    v = LSG.query(l, r)
    if B != v:
        print(-1)
        break
else:
    lsans = [LSG.leafvalue(i) for i in range(N)]
    print(*lsans)