#include #define int long long #define x first #define y second #define pi acos(-1) using namespace std; using LL = long long; using ULL = unsigned long long; typedef pair PII; const int N = 1e6 + 10, M = 5010, mod = 1e9 + 7; void solve() { int n; cin >> n; vector a(n + 1); int p = -1; unordered_map mp; int p2 = -1, p3 = -1; for(int i = 0; i < n; i++){ cin >> a[i]; if(a[i] == 0){ p = i; } if(mp[a[i]] != 0){ p2 = mp[a[i]]; p3 = i; } mp[a[i]] = i; } if(p != -1){ cout << 1 << "\n"; cout << p + 1 << "\n"; return; } if(p2 != -1){ cout << 2 << "\n"; cout << p2 + 1 << " " << p3 + 1 << "\n"; return; } vector d; for(int i = 0; i < n; i++){ int num = a[i], idx = (1LL << i); vector ans; for(auto [u, v]: d){ if((num ^ u) < num){ num = num ^ u; idx = idx ^ v; } } if(num == 0){ for(int j = 0; j <= 60; j++){ if((idx >> j) & 1) ans.push_back(j + 1); } cout << ans.size() << "\n"; for(auto c : ans) cout << c << " "; cout << "\n"; return; } d.push_back({num, idx}); } cout << -1 << "\n"; } signed main() { ios::sync_with_stdio(0),cin.tie(0),cout.tie(0); int T = 1; //cin >> T; while(T--) { solve(); } }