//
//  main.cpp
//  asm_contribute
//
//  Created by Qing Liu on 15/11/4.
//  Copyright © 2015年 Qing Liu. All rights reserved.
//

#include <iostream>
#include <cstring>
#include <cstdio>
#define maxn 1200
using namespace std;
bool used[1200];
int k[maxn],a[maxn];
int n;
void print(int t){
    cout<<t<<endl;
    for (int i=0; i<t; i++) {
        cout<<k[i]<<" ";
    }
}
bool DFS(int x,int s,int t){
    if (x==0) {
        print(t);
        return 1;
    }
    for (int i=s; i<n; i++) {
        k[t]=n-i;
        if (DFS(x^a[i], i+1, t+1)) {
            return 1;
        }
    }
    return 0;
}
int main() {
    freopen("asm_contribute.in", "r", stdin);
    freopen("asm_contribute.out", "w", stdout);
    cin>>n;
    for (int i=0; i<n; i++) {
        cin>>a[n-i-1];
    }
    for (int i=0; i<n; i++) {
        k[0]=n-i;
        if (DFS(a[i], i+1, 1)) {
            break;
        }
    }
    return 0;
}