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

void fast_io() {
    ios_base::sync_with_stdio(false);
    cin.tie(nullptr);
}

int main() {
    fast_io();
    int n;
    cin >> n;
    vector<long long> a(n);
    for (int i = 0; i < n; i++) {
        cin >> a[i];
    }
    for (int i = 0; i < n; i++) {
        if (a[i] == 0) {
            cout << 1 << endl << i + 1 << endl;
            return 0;
        }
    }
    vector<pair<long long, long long>> basis;
    for (int i = 0; i < n; i++) {
        long long val = a[i];
        long long idx = 1LL << i;
        for (auto [base, i] : basis) {
            if ((val ^ base) < val) {
                val ^= base;
                idx ^= i;
            }
        }
        if (val) {
            basis.push_back({val, idx});
        } else {
            vector<int> ans;
            for (int i = 0; i < 61; i++) {
                if (idx & (1LL << i)) {
                    ans.push_back(i + 1);
                }
            }
            cout << ans.size() << endl;
            for (int i : ans) {
                cout << i << " ";
            }
            cout << endl;
            return 0;
        }
    }
    cout << -1 << endl;
}