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: Wrong Answer)

gets
t = gets

a = t.split.map{|x| x.to_i}

if a.size == 1
  if a[0] == 1
    puts "1"
  else
    puts "-1"
  end
  exit
end

v = []
while a.size > 0
  j = 1
  flag = 0
  while j < a.size
    if (a[j] != j+1)
      v << a[j-1]
      a.delete_at(j-1)
      flag = 1
      break
    end
    j += 1
  end
  if flag == 0
    k = 0
    while k < a.size
      if (a[k] != k+1)
        puts "-1"
        exit
      end
      k +=1
    end
    a.each { |u|
      puts u
    }
    v.reverse.each { |u|
      puts u
    }
    exit
  end
end