#include<iostream>
#include<cstdio>
#include<algorithm>
#include<cmath>
#include<queue>
#include<vector>
#include<cstring>
#include<string>
#include<cstdlib>
using namespace std;
vector<long long> a;
vector<int> q;
int n;
bool ok=0;
void fun(int cur,long long x)
{
	
	if(x==0){
		
		cout<<q.size()<<endl;
		for(int i=0;i<q.size();i++)
		{
			cout<<q[i]+1<<" ";
		}
		ok=1;
		return;
	}
	if(cur==n) return;
	bool chedan=0;
	for(int i=0;i<q.size();i++)
	{
		if(a[cur]==a[i]) {
		chedan=1;
		break;
	}
	}
	if(chedan==0)
	{
	
	q.push_back(cur);
	fun(cur+1,x^a[cur]);
	q.pop_back();
	if(ok) return;
    }
	fun(cur+1,x);
	if(ok) return;
	
} 
int main()
{
	freopen("asm_contribute.in","r",stdin);
	freopen("asm_contribute.out","w",stdout);
	long long k;
	cin>>n;
	//long long k1=0,k2=0;
	for(int i=1;i<=n;i++)
	{
		scanf("%lld",&k);
		a.push_back(k);
	}
	for(int i=0;i<n;i++)
	{
		q.clear();
		k=a[i];
		q.push_back(i); 
		fun(1,k);
		
		if(ok) return 0;
	}
	return 0;
}