class DualSegmentTree:
    def __init__(self, n, segfunc, ide_ele):
        self.segfunc = segfunc
        self.ide_ele = ide_ele
        self.num = 1 << (n - 1).bit_length()
        self.tree = [ide_ele] * 2 * self.num

    def update(self,l,r,x):
        l += self.num
        r += self.num
        while l < r:
            if l & 1:
                self.tree[l] = self.segfunc(self.tree[l],x)
                l += 1
            if r & 1:
                self.tree[r-1] = self.segfunc(self.tree[r-1],x)
            l >>= 1
            r >>= 1

    def __getitem__(self,idx):
        idx += self.num
        res = self.ide_ele
        while idx:
            res = self.segfunc(res,self.tree[idx])
            idx>>=1
        return res

class SegmentTree:
    def __init__(self, init_val, segfunc, ide_ele):
        n = len(init_val)
        self.segfunc = segfunc
        self.ide_ele = ide_ele
        self.num = 1 << (n - 1).bit_length()
        self.tree = [ide_ele] * 2 * self.num
        self.size = n
        for i in range(n):
            self.tree[self.num + i] = init_val[i]
        for i in range(self.num - 1, 0, -1):
            self.tree[i] = self.segfunc(self.tree[2 * i], self.tree[2 * i + 1])

    def update(self, k, x):
        k += self.num
        self.tree[k] = x
        while k > 1:
            k >>= 1
            self.tree[k] = self.segfunc(self.tree[2*k], self.tree[2*k+1])

    def query(self, l, r):
        if r==self.size:
            r = self.num

        res = self.ide_ele

        l += self.num
        r += self.num
        right = []
        while l < r:
            if l & 1:
                res = self.segfunc(res, self.tree[l])
                l += 1
            if r & 1:
                right.append(self.tree[r-1])
            l >>= 1
            r >>= 1

        for e in right[::-1]:
            res = self.segfunc(res,e)
        return res

import sys,random

input = lambda :sys.stdin.readline().rstrip()
mi = lambda :map(int,input().split())
li = lambda :list(mi())

N,Q = mi()
A = DualSegmentTree(N,max,1)
query = [tuple(mi()) for i in range(Q)]
for l,r,b in query:
    A.update(l-1,r,b)

res = [A[i] for i in range(N)]
#print(res)
Seg = SegmentTree(res,min,10**17)
for l,r,b in query:
    if Seg.query(l-1,r)!=b:
        #print(Seg.query(l-1,r),b)
        exit(print(-1))

print(*res)