typedef long long ll;
typedef long double ld;

#include <bits/stdc++.h>
using namespace std;

signed main(){
    ll n;
    std::cin >> n;
    vector<ll> a(n);
    for (int i = 0; i < n; i++) {
        std::cin >> a[i];
    }
    int MAX_DIGITS=60;
    int N = n;
    int now = 0;
    auto &C = a;
    vector<ll> index(n);
    for (int i = 0; i < n; i++) {
        index[i] = i;
    }
    vector<vector<ll>> lo(n);
    for (int i = MAX_DIGITS; i >= 0; i--) {
        for (int j = now + 1; j < N; j++) {
            if (C[j] & (1ll << i)) {
                std::swap(C[now], C[j]);
                swap(index[now],index[j]);
                break;
            }
        }
        if (!(C[now] & (1ll << i))) continue;
        for (int j = 0; j < n; j++) {
            if (j != now && (C[j] & (1ll << i))){
                C[j] ^= C[now];
                lo[index[j]].push_back(index[now]);
            }
        }
        now++;
    }
    vector<ll> re(n);
    for (int i = 0; i < n; i++) {
        re[index[i]] = i;
    }
    for (int i = 0; i < n; i++) {
        if(a[re[i]]==0){
            std::cout << lo[i].size()+1 << std::endl;
            for (auto e : lo[i]) {
                std::cout << e+1<<" ";
            }
            std::cout << i+1 << std::endl;
            return 0;
        }else{
            
        }
    }
    std::cout << -1 << std::endl;
};