class segment_tree_dual:
    def __init__(self, N, compose, funcval, ID_M=None):
        self.compose = compose
        self.ID_M = ID_M
        self.funcval = funcval

        self.height = (N-1).bit_length() #木の段数
        self.N0 = 1<<self.height #木の横幅 >= N
        self.laz = [self.ID_M]*(2*self.N0) #作用素の木
        self.val = None #値の配列

    #初期値の配列を作る
    def build(self,initial):
        self.val = initial[:]

    #laz[k] を子に伝える、k が一番下の場合は laz[k] を val に反映する
    def propagate(self,k):
        if self.laz[k] == self.ID_M: return;
        if self.N0 <= k:
            self.val[k-self.N0] = self.funcval(self.val[k-self.N0], self.laz[k])
            self.laz[k] = self.ID_M
        else:
            self.laz[(k<<1)  ] = self.compose(self.laz[(k<<1)  ],self.laz[k]);
            self.laz[(k<<1)+1] = self.compose(self.laz[(k<<1)+1],self.laz[k]);
            self.laz[k] = self.ID_M;
    
    # 遅延をすべて解消する
    def propagate_all(self):
        upto = self.N0 + len(self.val)
        for i in range(1,upto): self.propagate(i)

    # laz[k]およびその上に位置する作用素をすべて伝播
    def thrust(self,k):
        for i in range(self.height,-1,-1): self.propagate(k>>i)

    # 区間[l,r]に関数 f を作用
    def update(self, L,R,f):
        L += self.N0; R += self.N0+1
        """まず伝播させる（オペレータが可換なら必要ない）"""
        #登りながら関数 f を合成
        while L < R:
            if R & 1:
                R -= 1
                self.laz[R] = self.compose(self.laz[R],f)
            if L & 1:
                self.laz[L] = self.compose(self.laz[L],f)
                L += 1
            L >>= 1; R >>= 1
    
    # values[k] を取得。
    def point_get(self, k):
        res = self.val[k]
        k += self.N0
        while k:
            if self.laz[k] != self.ID_M:
                res = self.funcval(res, self.laz[k])
            k //= 2
        return res
    
    # values[k] = x 代入する
    def point_set(self, k): 
        self.thrust(k+self.N0)
        self.val[k] = x




class segment_tree:
    __slots__ = ["op_M", "e_M","N","N0","dat"]
    def __init__(self, N, operator_M, e_M):
        self.op_M = operator_M
        self.e_M = e_M
        self.N = N
        self.N0 = 1<<(N-1).bit_length()
        self.dat = [self.e_M]*(2*self.N0)
    
    # 長さNの配列 initial で初期化
    def build(self, initial):
        assert self.N == len(initial)
        self.dat[self.N0:self.N0+len(initial)] = initial[:]
        for k in range(self.N0-1,0,-1):
            self.dat[k] = self.op_M(self.dat[2*k], self.dat[2*k+1])

    # a_k の値を x に更新
    def update(self,k,x):
        k += self.N0
        self.dat[k] = x
        k >>= 1
        while k:
            self.dat[k] = self.op_M(self.dat[2*k], self.dat[2*k+1])
            k >>= 1

    # 区間[L,R]をopでまとめる
    def query(self,L,R):
        L += self.N0; R += self.N0 + 1 
        sl = sr = self.e_M
        while L < R:
            if R & 1:
                R -= 1
                sr = self.op_M(self.dat[R],sr)
            if L & 1:
                sl = self.op_M(sl,self.dat[L])
                L += 1
            L >>= 1; R >>= 1
        return self.op_M(sl,sr)

    def get(self, k): #k番目の値を取得。query[k,k]と同じ
        return self.dat[k+self.N0]
    

n,Q = map(int,input().split())
lrb = [list(map(int,input().split())) for _ in range(Q)]

seg = segment_tree_dual(n+1, max, max, ID_M=1)
seg.build([1]*(n+1))
for l,r,b in lrb:
    seg.update(l,r,b)
seg.propagate_all()
res = seg.val

seg2 = segment_tree(n+1,min,1<<30)
seg2.build(res)
for l,r,b in lrb:
    if seg2.query(l,r) != b:
        print(-1)
        exit()
print(*res[1:])