Problem:
Score : 400 points

Problem Statement

There are N empty boxes arranged in a row from left to right.
The integer i is written on the i-th box from the left (1 \leq i \leq N).

For each of these boxes, Snuke can choose either to put a ball in it or to put nothing in it.

We say a set of choices to put a ball or not in the boxes is good when the following condition is satisfied:

For every integer i between 1 and N (inclusive), the total number of balls contained in the boxes with multiples of i written on them is congruent to a_i modulo 2.

Does there exist a good set of choices? If the answer is yes, find one good set of choices.

Constraints

All values in input are integers.

1 \leq N \leq 2 \times 10^5

a_i is 0 or 1.

Input

Input is given from Standard Input in the following format:

N
a_1 a_2 ... a_N

Output

If a good set of choices does not exist, print -1.

If a good set of choices exists, print one such set of choices in the following format:

M
b_1 b_2 ... b_M

where M denotes the number of boxes that will contain a ball, and b_1,\ b_2,\ ...,\ b_M are the integers written on these boxes, in any order.

Sample Input 1

3
1 0 0

Sample Output 1

1
1

Consider putting a ball only in the box with 1 written on it.

There are three boxes with multiples of 1 written on them: the boxes with 1, 2, and 3. The total number of balls contained in these boxes is 1.

There is only one box with a multiple of 2 written on it: the box with 2. The total number of balls contained in these boxes is 0.

There is only one box with a multiple of 3 written on it: the box with 3. The total number of balls contained in these boxes is 0.

Thus, the condition is satisfied, so this set of choices is good.

Sample Input 2

5
0 0 0 0 0

Sample Output 2

0

Putting nothing in the boxes can be a good set of choices.

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

import java.util.*;

public class Main{
    public static void main(String[] args) {
      Scanner sc = new Scanner(System.in);

      int n=sc.nextInt();

      n=n+1;

      int[] a = new int[n];

      for(int i=1;i<n;i++){
        a[i]=sc.nextInt();
      }

      int[] ans = new int[n];

      int sum1=0;
      int cnt=0;
      int flag=0;

      for(int i=n-1;i>=1;i--){
      //////////////////////////////////////////////////////
        if(n/2<=i){
          ans[i] = a[i];
        }
        else{
          cnt=i;
          for(int j=i;j<n;j+=cnt){
            sum1 = sum1 + a[j];
          }
          sum1 = sum1 % 2;
          //////////////////////////////////////////
          if(sum1==a[i]){
            ans[i] = sum1;
          }
          else{
            System.out.println("-1");
            flag = 1;
            break;
          }
          /////////////////////////////////////////
        }
      /////////////////////////////////////////////////////
      }

    if(flag==0){
    ////////////////////////////////////////
      int m=0;
      for(int i=1;i<n;i++){
        m = m + ans[i];
      }

      System.out.println(m);

      for(int i=1;i<n;i++){
        if(ans[i]==1){
          System.out.println(a[i]);
        }
      }
    /////////////////////////////////////////
    }

    }
}