#include<cstdio>
#include<vector>
#include<algorithm>
#include<queue>
#include<iostream>
#include<cstring>
using namespace std;
long long a[1010];
long long b[1010];
int tot;
int n;
bool dfs(int s)
{
	memset(b,0,sizeof(b));
	tot=0;
    for (int i=0;i<=n-1;i++)
    {
    	if ((s>>i)&1==1)
    	b[++tot]=i+1;
	}
	if (tot>1)
	{
		int p=a[b[1]];
		for (int i=2;i<=tot;i++)
		 p^=a[b[i]];
		if (!p) 
		 return true;	
	}
	return false;
}
int main()
{
	freopen("asm_contribute.in","r",stdin);
	freopen("asm_contribute.out","w",stdout);
	cin>>n;
	for (int i=1;i<=n;i++)
	 cin>>a[i];
    for (int i=1;i<(long long)(2<<n+1);i++)
     if (dfs(i))
     {
     	cout<<tot<<endl;
     	for (int j=1;j<=tot;j++)
     	 cout<<b[j]<<" ";
     	return 0;
	 }
}