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 Kotlin (1.0.0) (judge verdict: Accepted)

fun main(args: Array<String>) {
    agc032a()
}

fun agc032a() {
    val n = readLine()!!.toInt()
    val bList = readLine()!!.split(" ").map { it.toInt() }
        .toMutableList()

    if (bList.withIndex().any { iv ->
            val (index, b) = iv
            index + 1 < b
        }) return println(-1)

    val manipulation = mutableListOf<Int>()
    while (bList.isNotEmpty()) {
        val target = bList.withIndex().findLast { iv ->
            val (index, b) = iv
            index + 1 == b
        }
        if (target != null) {
            bList.removeAt(target.index)
            manipulation.add(target.value)
        } else return println(-1)
    }

    println(manipulation.reversed().joinToString(System.lineSeparator()))
}