#include<iostream>
#include<cstdio>
#include<cmath>
#include<cstring>
#include<algorithm>
using namespace std;
int n,a[1010],mem[1010],len;
void dfs(int s,int k){
	if(k==0){
		cout<<len<<endl;
		for(int i=1;i<=len;i++)
			cout<<mem[i]<<' ';
		cout<<endl;
		exit(0);
	}
	for(int i=s+1;i<=n;i++){
		int temp=k xor a[i];
		mem[++len]=i;
		dfs(i,temp);
		len--;
	}
}
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("%d",&a[i]);}
	for(int i=1;i<=n;i++){
		mem[++len]=i;
		dfs(i,a[i]);
		len--;
	}
	return 0;
}