def main():
  N,Q=map(int, input().split())
  INF =10**9
  LV = (N-1).bit_length()
  N0 = 2**LV
  data = [INF]*(2*N0)
  lazy = [None]*(2*N0)

  # 伝搬対象の区間を求める
  def gindex(l, r):
    L = (l + N0) >> 1; R = (r + N0) >> 1
    lc = 0 if l & 1 else (L & -L).bit_length()
    rc = 0 if r & 1 else (R & -R).bit_length()
    for i in range(LV):
        if rc <= i:
            yield R
        if L < R and lc <= i:
            yield L
        L >>= 1; R >>= 1

  # 遅延伝搬処理
  def propagates(*ids):
    for i in reversed(ids):
        v = lazy[i-1]
        if v is None:
            continue
        lazy[2*i-1] = data[2*i-1] = lazy[2*i] = data[2*i] = v
        lazy[i-1] = None

  # 区間[l, r)をxで更新
  def update(l, r, x):
    *ids, = gindex(l, r)
    propagates(*ids)

    L = N0 + l; R = N0 + r
    while L < R:
        if R & 1:
            R -= 1
            lazy[R-1] = data[R-1] = x
        if L & 1:
            lazy[L-1] = data[L-1] = x
            L += 1
        L >>= 1; R >>= 1
    for i in ids:
        data[i-1] = min(data[2*i-1], data[2*i])

  # 区間[l, r)内の最小値を求める（最大値の時はminをmaxに変えよう）
  def query(l, r):
    propagates(*gindex(l, r))
    L = N0 + l; R = N0 + r

    s = INF
    while L < R:
        if R & 1:
            R -= 1
            s = min(s, data[R-1])
        if L & 1:
            s = min(s, data[L-1])
            L += 1
        L >>= 1; R >>= 1
    return s

  B=[list(map(int, input().split())) for i in range(Q)]
  B=sorted(B,key=lambda x:x[2])
  for l,r,b in B:
    update(l-1,r,b)  
  for l,r,b in B:
    if b!=query(l-1,r):
      print(-1)
      exit()
    
  A=[]
  for i in range(N):
    A.append(query(i,i+1))
  print(*A)

if __name__ == '__main__':
    main()