#include <bits/stdc++.h>
//#include <atcoder/all>
using namespace std;
//using namespace atcoder;
//using mint = modint1000000007;
//const int mod = 1000000007;
//using mint = modint998244353;
//const int mod = 998244353;
//const int INF = 1e9;
//const long long LINF = 1e18;
#define rep(i, n) for (int i = 0; i < (n); ++i)
#define rep2(i,l,r)for(int i=(l);i<(r);++i)
#define rrep(i, n) for (int i = (n) - 1; i >= 0; --i)
#define rrep2(i,l,r)for(int i=(r) - 1;i>=(l);--i)
#define all(x) (x).begin(),(x).end()
#define allR(x) (x).rbegin(),(x).rend()
#define P pair<int,int>
template<typename A, typename B> inline bool chmax(A & a, const B & b) { if (a < b) { a = b; return true; } return false; }
template<typename A, typename B> inline bool chmin(A & a, const B & b) { if (a > b) { a = b; return true; } return false; }

int main() {
	ios::sync_with_stdio(false);
	cin.tie(nullptr);
	int n; cin >> n;
	vector<long long>a(n), b(n);
	rep(i, n)cin >> a[i];
	std::vector<long long>base;
	for (int i = 0; i < (int)a.size(); ++i) {
		auto ca = a[i];
		for (int j = 0; j < base.size(); ++j) {
			ca = std::min(ca, ca ^ base[j]);
		}
		if (ca == 0) {
			vector<int>ans = { i };
			rrep(j, i) {
				if (b[j] == (b[j] & a[i])) {
					ans.push_back(j);
				}
			}
			sort(all(ans));
			cout << ans.size() << endl;
			for (auto e : ans)cout << e + 1 << " ";
			cout << endl;
			return 0;
		}
		for (int j = 0; j < base.size(); ++j) {
			base[j] = std::min(base[j], ca ^ base[j]);
		}
		b[i] = ca;
		base.push_back(ca);
	}
	cout << -1 << endl;
	return 0;
}