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 C++14 (GCC 5.4.1) (judge verdict: Accepted)

#include <bits/stdc++.h>
using ll = long long;
using namespace std;
ll GCD(ll a, ll b) { return b ? GCD(b, a%b) : a; }
int main() {
    int n;
    cin>>n;
    vector<int> a(n+1);
    for(int i=1; i<=n; i++) cin>>a[i];
    vector<int> b(n+1);
    for(int i=n; i>1; i--){
        int ii=i,cnt=0;
        for(int j=2; j<=n; j++){
            if(j*i>n) break;
            cnt+=b[j*i];
        }
        if(a[i]&&cnt%2==0) b[i]++;
        else if(!a[i]&&cnt%2) b[i]++;
    }
    int x=0;
    int m=0;
    for(int i=2; i<=n; i++){
        x+=b[i];
        if(b[i]) m++;

    }
    if(a[1]&&x%2==0){
        b[1]++;
        m++;
    }else if(!a[1]&&x%2){
        b[1]++;
        m++;
    }
    cout<<m<<endl;
    for(int i=1; i<=n; i++){
        if(b[i]) cout<<i<<endl;
    }
}