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

INF = 10**9
B.sort(key=lambda x: (x[0], x[1]))
A = [INF for _ in range(n)]
min_ind = -1
for i in range(q):
    l, r, b = B[i]
    l -= 1
    r -= 1
    if l != min_ind:
        min_ind = l
    else:
        if b > A[min_ind]:
            print(-1)
            exit()
        min_ind += 1
        if min_ind > r:
            print(-1)
            exit()
    A[min_ind] = b
print(*A)