N,Q=map(int,input().split())
class LazySegTree_RUQ:
    #1-indexed
    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.lazy = [None]*2*self.num
        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 gindex(self,l,r):
        l += self.num
        r += self.num
        lm = l>>(l&-l).bit_length()
        rm = r>>(r&-r).bit_length()
        while r>l:
            if l<=lm:
                yield l
            if r<=rm:
                yield r
            r >>= 1
            l >>= 1
        while l:
            yield l
            l >>= 1
    def propagates(self,*ids):
        for i in reversed(ids):
            v = self.lazy[i]
            if v is None:
                continue
            self.lazy[i] = None
            self.lazy[2*i] = v
            self.lazy[2*i+1] = v
            self.tree[2*i] = v
            self.tree[2*i+1] = v

    # 区間[l, r)をxで更新
    def update(self,l,r,x):
        ids = self.gindex(l,r)
        self.propagates(*self.gindex(l,r))
        l += self.num
        r += self.num
        while l<r:
            if l&1:
                self.lazy[l] = x
                self.tree[l] = x
                l += 1
            if r&1:
                self.lazy[r-1] = x
                self.tree[r-1] = x
            r >>= 1
            l >>= 1
        for i in ids:
            self.tree[i] = self.segfunc(self.tree[2*i], self.tree[2*i+1])

    # 区間[l, r)内の何かを求める
    def query(self,l,r):
        ids = self.gindex(l,r)
        self.propagates(*self.gindex(l,r))
        res = self.ide_ele
        l += self.num
        r += self.num
        while l<r:
            if l&1:
                res = self.segfunc(res,self.tree[l])
                l += 1
            if r&1:
                res = self.segfunc(res,self.tree[r-1])
            l >>= 1
            r >>= 1
        return res
    
def segfunc(a,b):
    return min(a,b)
ide_ele=10**18

A=[10**9]*N
query=[]
for i in range(Q):
    l,r,B=map(int,input().split())
    query.append((B,l-1,r-1))
query.sort()
lst=LazySegTree_RUQ(A,segfunc,ide_ele)
for i in range(Q):
    B,l,r=query[i]
    lst.update(l,r+1,B)

flag=True
for i in range(Q):
    B,l,r=query[i]
    if lst.query(l,r+1)!=B:
        flag=False

if flag==False:
    print(-1)
    exit()
else:
    for i in range(N):
        A[i]=lst.query(i,i+1)
print(*A)