N, Q = map(int, input().split())
A = [list(map(int, input().split())) for _ in range(Q)]
for i in range(Q):
    A[i][0] -= 1


INF = 2*10**9
opX = max
opY = max
UnitX = -INF
UnitY = -INF
act = max


class LazySegmentTree():
    def __init__(self, n, opX, opY, UnitX, UnitY, A=None):
        self.s = 2**((n-1).bit_length())
        self.size = 2*self.s
        self.node = [UnitX]*self.size
        self.lazy = [UnitY]*self.size
        if A:
            for i in range(n):
                self.node[self.s+i] = A[i]
            for i in range(self.s-1, -1, -1):
                self.node[i] = opX(self.node[2*i], self.node[2*i+1])

    def propagation(self, i):
        h = i.bit_length()-1
        for n in range(h, 0, -1):
            j = i >> n
            if self.lazy[j] != UnitY:
                self.node[j] = act(self.node[j], self.lazy[j])
                self.lazy[2*j] = opY(self.lazy[2*j], self.lazy[j])
                self.lazy[2*j+1] = opY(self.lazy[2*j+1], self.lazy[j])
                self.lazy[j] = UnitY

    def recalculate(self, i):
        while i > 1:
            i >>= 1
            x = act(self.node[2*i], self.lazy[2*i])
            y = act(self.node[2*i+1], self.lazy[2*i+1])
            self.node[i] = opX(x, y)

    def update_range(self, L, R, a):
        L += self.s
        R += self.s
        L0 = L//(L & -L)
        R0 = R//(R & -R)
        self.propagation(L0)
        self.propagation(R0)
        while L < R:
            if L & 1:
                self.lazy[L] = opY(self.lazy[L], a)
                L += 1
            if R & 1:
                R -= 1
                self.lazy[R] = opY(self.lazy[R], a)
            L >>= 1
            R >>= 1
        self.recalculate(L0)
        self.recalculate(R0)

    def get_range(self, L, R):
        vL, vR = UnitX, UnitX
        L += self.s
        R += self.s
        L0 = L//(L & -L)
        R0 = R//(R & -R)
        self.propagation(L0)
        self.propagation(R0)
        while L < R:
            if L & 1:
                vL = opX(vL, act(self.node[L], self.lazy[L]))
                L += 1
            if R & 1:
                R -= 1
                vR = opX(act(self.node[R], self.lazy[R]), vR)
            L >>= 1
            R >>= 1
        return opX(vL, vR)


state = LazySegmentTree(N, max, max, -INF, -INF)
for l, r, v in A:
    state.update_range(l, r, v)

seq = [state.get_range(i, i+1) for i in range(N)]
for i in range(N):
    if seq[i] == -INF:
        seq[i] = 1
opX = min
opY = min
UnitX = INF
UnitY = INF
act = min
solve = LazySegmentTree(N, min, min, INF, INF, seq)

for l, r, v in A:
    if solve.get_range(l, r) != v:
        print(-1)
        break
else:
    print(*seq)