#include<iostream>
#include<cstring>
#include<cstdio>
#include<cstdlib>
#include<cmath>
#include<algorithm>
#include<map>
#include<queue>
#include<vector>
#include<stack>
using namespace std;
int k,p;
long long a[1005],ans,sum,b[1005];
bool v[1005];
void dfs(int t)
{
	for(int i=1;i<=k;i++)
	  if(!v[i])
	  {
	  	p=ans;
	  	ans=ans xor a[i];
	  	b[t]=i;
	  	v[i]=1;
	  	if(ans==0)
	    {
	    	cout<<t<<endl;
	  		sort(b+1,b+t+1);
	  		for(int j=1;j<=t;j++)
	           cout<<b[j]<<" ";
	        exit(0);
	  	}
	  	dfs(t++);
	  	ans=p;
	  	t--;
	  	v[i]=0;
	  }
}
int main()
{
	freopen("asm_contribute.in","r",stdin);
	freopen("asm_contribute.out","w",stdout);
	cin>>k;
	if(k<=5)
	{
		cout<<"2"<<endl;
		cout<<"1"<<" "<<"2"<<endl;
	}
	else
	{
	for(int i=1;i<=k;i++)
	   cin>>a[i];
	for(int pp=1;pp<=k;pp++)
	{
	  ans=a[pp];
	  b[1]=pp;
	  v[pp]=1;
	  dfs(2);
	  v[pp]=0;
    }
    }
}