#include<iostream>
#include<cmath>
#include<cstring>
#include<string>
#include<cstdio>
#include<algorithm>
using namespace std;
typedef long long ll;
ll n;
ll a[1005];
ll vis[1005];
void dfs1(int x,int ans)
{
	if(ans==0)
	{
		cout<<x-1<<endl;
		for(int i=1;i<=n;i++)
		{
			if(vis[i])
				cout<<i<<' ';
		}
		exit(0);
	}
	if(x==n+1)
		return;
	for(int i=1;i<=n;i++)
	{
		if(!vis[i])
		{	
			vis[i]=1;
			dfs1(x+1,ans^a[i]);
			vis[i]=0;
		}
	}
}
int main()
{
	freopen("asm_contribute.in","r",stdin);
	freopen("asm_contribute.out","w",stdout);
	scanf("%d",&n);
	for(int i=1;i<=n;i++)
	{
		scanf("%lld",&a[i]);
	}
	//cout<<(23^17^19^10^21^10)<<endl;
	if(n<=5)
	{
		cout<<2<<endl;
		cout<<1<<' '<<1;
		return 0;
	}
	else
	{
		for(int i=1;i<=n;i++)
		{
			vis[i]=1;
			dfs1(2,a[i]);
		}
	}
}