from sys import stdin, stdout
from math import sqrt, pi, acos, gcd, atan2, cos, sin, factorial
from decimal import Decimal
from random import randint
from matplotlib import mlab
from matplotlib import pylab
PEPS = 1e-10
INF = float('inf')


def sqr(a):
    return a * a


def dist(a, b = (0, 0)):
    return sqrt(sqr(a[0] - b[0]) + sqr(a[1] - b[1]))


def s_dist(a, b = (0, 0)):
    return (sqr(a[0] - b[0]) + sqr(a[1] - b[1]))


def dist3(a, b = (0, 0, 0)):
    return sqrt(sqr(a[0] - b[0]) + sqr(a[1] - b[1]) + sqr(a[2] - b[2]))


def s_dist3(a, b = (0, 0, 0)):
    return (sqr(a[0] - b[0]) + sqr(a[1] - b[1]) + sqr(a[2] - b[2]))


def trans(p, al):
    return (p[0] * cos(al) + p[1] * sin(al), - p[0] * sin(al) + p[1] * cos(al))


def get_angle(a, b, c):
    cos_al = (sqr(a) + sqr(b) - sqr(c)) / (2 * a * b)
    return acos(cos_al)


def write_float(ans):
    stdout.write(str('%.13f' % ans) + '\n')


def get_hight(pt1, pt2, pt3):
    a = (pt2[0] - pt1[0], pt2[1] - pt1[1])
    b = (pt3[0] - pt1[0], pt3[1] - pt1[1])
    return abs(a[0] * b[1] - a[1] * b[0]) / dist(pt1, pt2)


def get_square(pt1, pt2, pt3):
    a = (pt2[0] - pt1[0], pt2[1] - pt1[1])
    b = (pt3[0] - pt2[0], pt3[1] - pt2[1])
    return (a[0] * b[-1] - a[1] * b[0]) / 2


def sign(v):
    if v > 0:
        return 1
    elif v < 0:
        return -1
    else:
        return 0


def inn(pt, triangle):
    signs = set()
    signs.add(sign(get_square(triangle[0], triangle[1], pt)))
    signs.add(sign(get_square(triangle[1], triangle[2], pt)))
    signs.add(sign(get_square(triangle[2], triangle[0], pt)))
    return len(signs) == 1


def inter_in(a, b):
    return dist((a[0], a[1]), (b[0], b[1])) < a[-1] + b[-1]


def inter_in3(a, b):
    return dist3(a[:-1], b[:-1]) < a[-1] + b[-1]


def shift(what, wth):
    return (what[0] - wth[0], what[1] - wth[1])


n = int(stdin.readline())
vl = list(map(int, stdin.readline().split()))
ans = []

while len(vl):
    for i in range(len(vl) - 1, -1, -1):
        if vl[i] == i + 1:
            ans.append(i + 1)
            vl = vl[:i] + vl[i + 1:]
            break
    else:
        stdout.write('-1\n')
        break


if len(ans) == n:
    ans = ans[::-1]
    stdout.write(' '.join(list(map(str, ans))))

### FIXED CODE ###

from sys import stdin, stdout
from decimal import Decimal
from random import randint
PEPS = 1e-10
INF = float('inf')


def sqr(a):
    return a * a


def dist(a, b = (0, 0)):
    return sqrt(sqr(a[0] - b[0]) + sqr(a[1] - b[1]))


def s_dist(a, b = (0, 0)):
    return (sqr(a[0] - b[0]) + sqr(a[1] - b[1]))


def dist3(a, b = (0, 0, 0)):
    return sqrt(sqr(a[0] - b[0]) + sqr(a[1] - b[1]) + sqr(a[2] - b[2]))


def s_dist3(a, b = (0, 0, 0)):
    return (sqr(a[0] - b[0]) + sqr(a[1] - b[1]) + sqr(a[2] - b[2]))


def trans(p, al):
    return (p[0] * cos(al) + p[1] * sin(al), - p[0] * sin(al) + p[1] * cos(al))


def get_angle(a, b, c):
    cos_al = (sqr(a) + sqr(b) - sqr(c)) / (2 * a * b)
    return acos(cos_al)


def write_float(ans):
    stdout.write(str('%.13f' % ans) + '\n')


def get_hight(pt1, pt2, pt3):
    a = (pt2[0] - pt1[0], pt2[1] - pt1[1])
    b = (pt3[0] - pt1[0], pt3[1] - pt1[1])
    return abs(a[0] * b[1] - a[1] * b[0]) / dist(pt1, pt2)


def get_square(pt1, pt2, pt3):
    a = (pt2[0] - pt1[0], pt2[1] - pt1[1])
    b = (pt3[0] - pt2[0], pt3[1] - pt2[1])
    return (a[0] * b[-1] - a[1] * b[0]) / 2


def sign(v):
    if v > 0:
        return 1
    elif v < 0:
        return -1
    else:
        return 0


def inn(pt, triangle):
    signs = set()
    signs.add(sign(get_square(triangle[0], triangle[1], pt)))
    signs.add(sign(get_square(triangle[1], triangle[2], pt)))
    signs.add(sign(get_square(triangle[2], triangle[0], pt)))
    return len(signs) == 1


def inter_in(a, b):
    return dist((a[0], a[1]), (b[0], b[1])) < a[-1] + b[-1]


def inter_in3(a, b):
    return dist3(a[:-1], b[:-1]) < a[-1] + b[-1]


def shift(what, wth):
    return (what[0] - wth[0], what[1] - wth[1])


n = int(stdin.readline())
vl = list(map(int, stdin.readline().split()))
ans = []

while len(vl):
    for i in range(len(vl) - 1, -1, -1):
        if vl[i] == i + 1:
            ans.append(i + 1)
            vl = vl[:i] + vl[i + 1:]
            break
    else:
        stdout.write('-1\n')
        break


if len(ans) == n:
    ans = ans[::-1]
    stdout.write('\n'.join(list(map(str, ans))))