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 C (GCC 5.4.1) (judge verdict: Accepted)

#include <stdio.h>

int main(){
  int b[100];
  int n;
  int score;
  scanf("%d\n",&n);
  for(int i=0; i<n; i++) {
    scanf("%d",&b[i]);
    if(b[i]>i+1) {
      printf("-1");
      return 0;
    }
  }
  for(int i=0; i<n;i++){
    for(int j=n-1; j>=0; j--){
      score = 1;
      if(b[j] > n) continue;
      for(int k=j-1; k>=0; k--){
        if(b[k]==200) score++;
      }
      if(score == b[j]) {
        printf("%d\n",b[j]);
        b[j] = 200;
        break;
      }
    }
  }     
  return 0;
}