#include <bits/stdc++.h>
using namespace std;
using ll = long long;
#define ALL(v) v.begin(),v.end()
#define dbg(x) cerr << #x << ": " << (x) << endl;
int N;
vector<ll>A;
int main() {
    cin >> N;
    A.resize(N);
    for (int i = 0; i < N; ++i) cin >> A[i];
    auto cp = A;
    
    vector<int> ans;
    vector<ll> idx(N);
    for (int i = 0; i < min(61,N); ++i) {
        idx[i] = 1LL << i;
    }
    int pos = 0;
    for (int j = 0; j < 60; ++j) {
        bool fn = false;
        for (int i = pos; i < N; ++i) {
            if (A[i] >> j & 1) {
                swap(A[i], A[pos]);
                swap(idx[i], idx[pos]);
                fn = true;
                break;
            }
        }
        if (fn) {
            for (int i = 0; i < N; ++i) {
                if (i != pos && (A[i] >> j & 1)) {
                    A[i] ^= A[pos];
                    idx[i] ^= idx[pos];
                }
            }
            ++pos;
        }
    }
    for (int i = 0; i < N; ++i) {
        if (A[i] == 0) {
            vector<int>ans;
            for (int j = 0; j <= 60; ++j) {
                if (idx[i] >> j & 1) {
                    ans.push_back(j);
                }
            }
            cout << ans.size() << '\n';
            for (int j = 0; j < ans.size(); ++j) {
                cout << ans[j]+1 << " \n"[j==ans.size()-1];
            }
            return 0;
        }
    }
    cout << -1 << '\n';
}