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 Java8 (OpenJDK 1.8.0) (judge verdict: Wrong Answer)

import java.util.ArrayList;
import java.util.Scanner;
public class Main {

	public static void main(String[] args) {

		Scanner sc = new Scanner(System.in);

		int N = sc.nextInt();

		ArrayList<Integer> array = new ArrayList<>();

		for(int i=0;i<N;i++) {

			int b = sc.nextInt();

			array.add(b);

		}

		if(array.get(0) != 1) System.out.println(-1);

		else {

			ArrayList<Integer> ans = new ArrayList<>();

			int count = 0;

			boolean flag;

			while(count<N) {

				flag = false;

				for(int i=array.size()-1;i>0;i--) {

					if(array.get(i) == i+1) {

						ans.add(i+1);

						array.remove(i);

						flag = true;

						break;
					}
				}

				if(!flag &&array.size()>1) {

					if(array.get(1) == 1) {

						ans.add(1);

						array.remove(1);

						//continue;
					}
				}
				count++;
			}

			if(ans.size()!=N-1 && array.get(0)!=1) {

				System.out.println(-1);

			}else {

				System.out.println(1);

				for(int i=ans.size()-1;i>=0;i--) {

					System.out.println(ans.get(i));
				}
			}
		}
	}

}