from collections import defaultdict
import sys
input = sys.stdin.buffer.readline
sys.setrecursionlimit(10 ** 7)


class UF_tree:
    def __init__(self, n):
        self.root = [-1] * (n + 1)

    def find(self, x):
        stack = []
        while self.root[x] > 0:
            stack.append(x)
            x = self.root[x]
        for i in stack:
            self.root[i] = x
        return x

    def isSame(self, x, y):
        return self.find(x) == self.find(y)

    def unite(self, x, y):
        x = self.find(x)
        y = self.find(y)
        if x == y:
            return False
        if x < y:
            x, y = y, x
        self.root[x] += self.root[y]
        self.root[y] = x
        return True

    def size(self, x):
        return -self.root[self.find(x)]


def main():
    d = defaultdict(list)
    val = set()
    N, Q = map(int, input().split())
    for _ in range(Q):
        L, R, B = map(int, input().split())
        val.add(B)
        d[B].append((L, R))

    ans = [-1] * N
    uf = UF_tree(N)
    for v in sorted(val, reverse=True):
        for l, r in d[v]:
            l -= 1
            l = uf.find(l)
            if l < r:
                if ans[l] < 0:
                    ans[l] = v
            else:
                print(-1)
                return
        for l, r in d[v]:
            l -= 1
            l = uf.find(l)
            while l < r:
                uf.unite(l, l+1)
                l = uf.find(l)

    for i in range(N):
        if ans[i] < 0:
            ans[i] = 10 ** 9
    print(*ans)
    return


main()