#include <iostream>
#include <cstdio>
#include <algorithm>
#include <cstring>
#include <string>
#include <cmath>
#include <iomanip>
using namespace std;
long long n,a[1010],t=0;
bool flag=0,f[1010];
void dfs(int k,long long ans)
{
	if (!ans&&t) flag=1;
	if (flag||k>n) return;
	dfs(k+1,ans);
	if (flag) return;
	f[k]=1;
	if (ans)
	{
		t++;
		dfs(k+1,ans^a[k]);
		if (flag) return;
		t--;
	}
	else
	{
		t++;
		dfs(k+1,a[k]);
		if (flag) return;
		t--;
	}
	f[k]=0;
}
int main()
{
	freopen("asm_contribute.in","r",stdin);
	freopen("asm_contribute.out","w",stdout);
	ios::sync_with_stdio(false);
	cin>>n;
	for (int i=1;i<=n;i++)
		cin>>a[i];
	dfs(1,0);
	cout<<t<<endl;
	for (int i=1;i<=n;i++)
		if (f[i]) cout<<i<<' ';
	fclose(stdin);
	fclose(stdout);
	return 0;
}