Problem:
Score : 400 points

Problem Statement

Snuke has an empty sequence a.

He will perform N operations on this sequence.

In the i-th operation, he chooses an integer j satisfying 1 \leq j \leq i, and insert j at position j in a (the beginning is position 1).

You are given a sequence b of length N. Determine if it is possible that a is equal to b after N operations. If it is, show one possible sequence of operations that achieves it.

Constraints

All values in input are integers.

1 \leq N \leq 100

1 \leq b_i \leq N

Input

Input is given from Standard Input in the following format:

N
b_1 \dots b_N

Output

If there is no sequence of N operations after which a would be equal to b, print -1.
If there is, print N lines. In the i-th line, the integer chosen in the i-th operation should be printed. If there are multiple solutions, any of them is accepted.

Sample Input 1

3
1 2 1

Sample Output 1

1
1
2

In this sequence of operations, the sequence a changes as follows:

After the first operation: (1)

After the second operation: (1,1)

After the third operation: (1,2,1)

Sample Input 2

2
2 2

Sample Output 2

-1

2 cannot be inserted at the beginning of the sequence, so this is impossible.

Sample Input 3

9
1 1 1 2 2 1 2 3 2

Sample Output 3

1
2
2
3
1
2
2
1
1

Solution in Ruby (2.3.3) (judge verdict: Accepted)

N = (gets).to_i
bs = (gets).split(" ").map {|i| i.to_i}

=begin
* つまり与えられた配列をいいかんじに空にするルールを作らないといけない
* i番目にiを挿入するのだから、その逆回しで、i番目からiを摘出する手順を行う
=end

res = []
isOK = true
while (bs.length > 0) && isOK
    isOK = false # ひとつも取り除けなかったら終わる
    (bs.length-1).downto(0) do |i|
        if bs[i] == i+1 then
            res << i+1
            bs.delete_at(i)
            isOK = true
            break
        end
    end
end

if isOK then
    puts res.reverse # 取り除く順番の逆なので
else
    puts "-1"
end