#include<cstdio>
#include<iostream>
using namespace std;
typedef long long LL;
const int SIZEN=1010;
int N;
LL A[SIZEN];
LL ans[SIZEN]={0};
int tot=0;
void read()
{
	scanf("%d",&N);
	for(int i=1;i<=N;i++)
	{
		//scanf("%I64d",&A[i]);
		scanf("%lld",&A[i]);
	}
}
bool dfs(int x,int now)
{
	if(x!=0&&now==0)
	{
		return 1;
	}
	for(int i=x+1;i<=N;i++)
	{
		tot++;
		ans[tot]=i;
		if(dfs(i,now^A[i])) return 1;
		tot--;
	}
	return 0;
}
void work()
{
	dfs(0,tot);
	printf("%d\n",tot);
	for(int i=1;i<=tot;i++) printf("%lld ",ans[i]);
}
int main()
{
	freopen("asm_contribute.in","r",stdin);
	freopen("asm_contribute.out","w",stdout);
	read();
	work();
	return 0;
}