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

#define rep2(i, m, n) for (int i = (m); i < (n); ++i)
#define rep(i, n) rep2(i, 0, n)
#define drep2(i, m, n) for (int i = (m)-1; i >= (n); --i)
#define drep(i, n) drep2(i, n, 0)
#define all(...) std::begin(__VA_ARGS__), std::end(__VA_ARGS__)
#define rall(...) std::rbegin(__VA_ARGS__), std::rend(__VA_ARGS__)
#define FOR(i, a, b) for (int i = (a), i##_len = (b); i <= i##_len; ++i)
#define REV(i, a, b) for (int i = (a); i >= (b); --i)
#define CLR(a, b) memset((a), (b), sizeof(a))
#define DUMP(x) cout << #x << " = " << (x) << endl;
#define INF 1001001001001001001ll
#define inf (int)1001001000
#define MOD 998244353
#define MOD1 1000000007
#define PI 3.14159265358979
#define Dval 1e-12
#define fcout cout << fixed << setprecision(12)
#define Mp make_pair
#define pb push_back
#define fi first
#define se second
#define SORT(x) sort(x.begin(),x.end())
#define ERASE(x) x.erase(unique(x.begin(),x.end()),x.end())
#define POSL(x,v) (distance(x.begin(),lower_bound(x.begin(),x.end(),v)-x.begin()))
#define POSU(x,v) (distance(x.begin(),upper_bound(x.begin(),x.end(),v)-x.begin()))

using ll = long long;
using ld = long double;
using vi = vector<int>;
using vl = vector<long long>;
using vs = vector<string>;
using vd = vector<double>;
using vld = vector<long double>;
using vc = vector<char>;
using vb = vector<bool>;
using vpii = vector<pair<int, int>>;
using vpil = vector<pair<int, long long>>;
using vpll = vector<pair<long long, long long>>;
using vvi = vector<vector<int>>;
using vvl = vector<vector<long long>>;
using vvd = vector<vector<double>>;
using vvld = vector<vector<long double>>;
using vvc = vector<vector<char>>;
using vvb = vector<vector<bool>>;
using vvpii = vector<vector<pair<int,int>>>;
using vvpll = vector<vector<pair<long long,long long>>>;
using vvvi = vector<vector<vector<int>>>;
using vvvl = vector<vector<vector<long long>>>;
using pii = pair<int, int>;
using pll = pair<long long, long long>;
using LL = __int128_t;
using mint = atcoder::modint998244353;
using vmint = vector<mint>;
using vvmint = vector<vector<mint>>;
using vvvmint = vector<vector<vector<mint>>>;

ll gcd(ll x, ll y) {	if (x == 0) return y;	return gcd(y%x, x);} ll lcm(ll x, ll y) { __int128_t xx,yy; xx=x; yy=y; __int128_t ans=xx * yy / gcd(x, y); ll ans2=ans; return ans; }
template<typename T>
T POW(T x, ll n){T ret=1;	while(n>0){		if(n&1) ret=ret*x;		x=x*x;		n>>=1;	}	return ret;}
template<typename T>
T modpow(T a, ll n, T p) {	if(n==0) return (T)1;  if (n == 1) return a % p;  if (n % 2 == 1) return (a * modpow(a, n - 1, p)) % p;  T t = modpow(a, n / 2, p);  return (t * t) % p;}
template<typename T>
T modinv(T a, T m) {	if(m==0)return (T)1;	T b = m, u = 1, v = 0;	while (b) {		T t = a / b;		a -= t * b; swap(a, b);		u -= t * v; swap(u, v);	}	u %= m;	if (u < 0) u += m;	return u;}
template<typename T>
T REM(T a, T b){ return (a % b + b) % b;}
template<typename T>
T QUO(T a, T b){ return (a - REM(a, b)) / b;}
ll rand_int(ll l, ll r) { //[l, r]
	//#ifdef LOCAL
	static mt19937_64 gen;
	/*#else
	static mt19937_64 gen(chrono::steady_clock::now().time_since_epoch().count());
	#endif*/
	return uniform_int_distribution<ll>(l, r)(gen);
}
/* 
const int MAXCOMB=510000;
ll MODCOMB = 998244353;
ll fac[MAXCOMB], finv[MAXCOMB], inv[MAXCOMB]; 
void COMinit() {	fac[0] = fac[1] = 1;	finv[0] = finv[1] = 1;	inv[1] = 1;	for (int i = 2; i < MAXCOMB; i++) {		fac[i] = fac[i - 1] * i % MODCOMB;		inv[i] = MODCOMB - inv[MODCOMB%i] * (MODCOMB / i) % MODCOMB;		finv[i] = finv[i - 1] * inv[i] % MODCOMB;	}}
ll COM(ll n, ll k) {	if (n < k) return 0;	if (n < 0 || k < 0) return 0;	return fac[n] * (finv[k] * finv[n - k] % MODCOMB) % MODCOMB;}
ll com(ll n,ll m){   if(n<m || n<=0 ||m<0){		return 0;	}	if( m==0 || n==m){		return 1;	}	ll k=1;	for(ll i=1;i<=m;i++){       k*=(n-i+1); 	   k%=MODCOMB;	   k*=modinv(i,MODCOMB);	   k%=MODCOMB;	}	return k;}
*/

const int MAXCOMB=510000;
std::vector<mint> FAC(MAXCOMB), FINV(MAXCOMB), INV(MAXCOMB);
void COMinit() {FAC[0] = FAC[1] = 1;FINV[0] = FINV[1] = 1;INV[1] = 1;for (int i = 2; i < MAXCOMB; i++) {FAC[i] = FAC[i - 1] * i;INV[i] = mint(0) - INV[mint::mod() % i] * (mint::mod() / i);FINV[i] = FINV[i - 1] * INV[i];}}
mint COM(int n, int k) {if (n < k) return 0;if (n < 0 || k < 0) return 0;return FAC[n] * FINV[k] * FINV[n - k];}

template <typename T> inline bool chmax(T &a, T b) { return ((a < b) ? (a = b, true) : (false));}
template <typename T> inline bool chmin(T &a, T b) { return ((a > b) ? (a = b, true) : (false));}
template <class T> T BS(vector<T> &vec, T key) { auto itr = lower_bound(vec.begin(), vec.end(), key); return distance(vec.begin(), itr); }
template<class T> pair<T,T> RangeBS(vector<T> &vec, T lowv, T highv){auto itr_l = lower_bound(vec.begin(), vec.end(), lowv); auto itr_r = upper_bound(vec.begin(), vec.end(), highv); return make_pair(distance(vec.begin(), itr_l), distance(vec.begin(), itr_r)-1);}
void fail() { cout << "-1\n"; exit(0); } void no() { cout << "No\n"; exit(0); } void yes() { cout << "Yes\n"; exit(0); }
template<class T> void er(T a) { cout << a << '\n'; exit(0); }
int dx[] = { 1,0,-1,0,1,1,-1,-1 }; int dy[] = { 0,1,0,-1,1,-1,1,-1};
bool range_in(int i, int j, int h, int w){ if(i<0 || j<0 || i>=h || j>=w) return false; return true;} 
int bitcount(int n){n=(n&0x55555555)+(n>>1&0x55555555); n=(n&0x33333333)+(n>>2&0x33333333); n=(n&0x0f0f0f0f)+(n>>4&0x0f0f0f0f); n=(n&0x00ff00ff)+(n>>8&0x00ff00ff); n=(n&0x0000ffff)+(n>>16&0x0000ffff); return n;}

template<typename T>
struct Edge{
    int from, to, index;
    T cost;
    Edge() : from(-1), to(-1), index(-1), cost(0) {}
    Edge(int _to) : from(-1), to(_to), index(-1), cost(0) {}
    Edge(int _to, T _cost) : from(-1), to(_to), index(-1), cost(_cost) {}
    Edge(int _from, int _to, int _index) : from(_from), to(_to), index(_index), cost(0) {}
    Edge(int _from, int _to, int _index, T _cost) 
        : from(_from), to(_to), index(_index), cost(_cost) {}
    bool operator<(const Edge<T>& other) const {
        return cost < other.cost; 
    }
    Edge &operator=(const int &x) {
        to = x;
        return *this;
    }
    operator int() const { return to; }
};
using Graph = vector<vector<int>>; 
template <typename T>
using WGraph = vector<vector<Edge<T>>>; 


//////////////////////////////////////////////////////////////////////////////////////////


namespace std {
template <size_t N>
bool operator<(const bitset<N> &a, const bitset<N> &b) {
  int f = (a ^ b)._Find_first();
  return f == N ? false : a[f];
}
}  // namespace std

template <size_t H_MAX, size_t W_MAX>
struct F2_Matrix {
  using Mat = F2_Matrix;

  int H, W;
  array<bitset<W_MAX>, H_MAX> A;
  vector<vector<int>> index;
  vector<int> firsth;

  F2_Matrix(int h = H_MAX, int w = W_MAX) : H(h), W(w), index(H_MAX), firsth(H_MAX) {
    assert(0 <= h and h <= (int)H_MAX);
    assert(0 <= w and w <= (int)W_MAX);
    for (int i = 0; i < (int)H_MAX; i++) A[i].reset();
    for(int i=0;i<(int)H_MAX;i++)firsth[i]=i;
  }
  inline bitset<W_MAX> &operator[](int i) { return A[i]; }
  inline const bitset<W_MAX> &operator[](int i) const { return A[i]; }

  static Mat I(int n) {
    Mat a(n, n);
    for (int i = 0; i < n; i++) a[i][i] = true;
    return a;
  }



  // (AND, XOR) 半環
  // (AND, OR) 半環には operator/ を割り当てた
  Mat &operator*=(const Mat &B) {
    Mat C(H, B.W);
    for (int i = 0; i < H; i++) {
      for (int j = 0; j < W; j++) {
        if (A[i][j]) C[i] ^= B[j];
      }
    }
    swap(A, C.A);
    return *this;
  }
  Mat operator*(const Mat &B) const { return Mat(*this) *= B; }

  // (AND, OR) 半環
  friend Mat and_or_product(const Mat &A, const Mat &B) {
    Mat C(A.H, B.W);
    for (int i = 0; i < A.H; i++) {
      for (int j = 0; j < A.W; j++) {
        if (A[i][j]) C[i] |= B[j];
      }
    }
    return C;
  }

  // [0, wr) の範囲で列を掃き出し, rank を返す(0列目からwr-1列目までの列ベクトルから生成される空間の次元)
  pair<vector<vector<int>>,vector<int>> sweep(int wr = -1) {
    if (wr == -1) wr = W;
    int t = 0;
    for (int u = 0; u < wr; u++) {
      int piv = -1;
      for (int i = t; i < H; i++) {
        if (A[i][u]) {
          piv = i;
          break;
        }
      }
      if (piv == -1) continue;
      if (piv != t) {swap(A[piv], A[t]); swap(index[piv],index[t]); swap(firsth[piv],firsth[t]);}
      for (int i = 0; i < H; i++) {
        if (i != t && A[i][u]) {A[i] ^= A[t]; index[i].pb(t);
      }
      }
      t++;
    }

    return make_pair(index,firsth);
  
  }

  Mat inverse() const {
    assert(H == W);
    int N = H;
    F2_Matrix<H_MAX, W_MAX * 2> c(H, W * 2);
    for (int i = 0; i < N; i++) {
      c[i][i + N] = 1;
      for (int j = 0; j < N; j++) {
        c[i][j] = A[i][j];
      }
    }
    int r = c.sweep();
    assert(r == N);
    Mat b(H, W);
    for (int i = 0; i < N; i++) {
      for (int j = 0; j < N; j++) {
        b[i][j] = c[i][j + N];
      }
    }
    return b;
  }

  int determinant() const {
    assert(H == W);
    F2_Matrix<H_MAX, W_MAX> c{*this};
    int r = c.sweep();
    return r == H ? 1 : 0;
  }

  bool operator<(const Mat &rhs) const {
    if (H != rhs.H) return H < rhs.H;
    if (W != rhs.W) return W < rhs.W;
    return A < rhs.A;
  }
  bool operator==(const Mat &rhs) const {
    return H == rhs.H and W == rhs.W and A == rhs.A;
  }

  friend ostream &operator<<(ostream &os, const Mat &b) {
    for (int i = 0; i < b.H; i++) {
      os << "[ ";
      for (int j = 0; j < b.W; j++) {
        os << b[i][j] << ", ";
      }
      os << "],\n";
    }
    return os;
  }
};


void solve(){
    int N;
    cin>>N;
    const int n= N;
    vl a(n);
    rep(i,n){
        cin>>a[i];
    }
    
    int h=min(n,61);
    int W=60;
    F2_Matrix<61,60> mat;
    rep(i,h){
        mat[i]=a[i];
    }
    auto index=mat.sweep();

    rep(i,min(61,n)){
        if(mat[i]==0 && index.se[i]<h){
            cout<<index.fi[i].size()+1<<endl;
            for(int to:index.fi[i]){
                cout<<to+1<<" ";
            }
            cout<<index.se[i]+1<<endl;
            return;
        }
    }

    cout<<-1<<endl;
    


    
}

signed main(){
	cin.tie(0);
	ios::sync_with_stdio(0);
	cout<<fixed<<setprecision(20);
	int TT; TT = 1; //cin >> TT;
	while(TT--) solve();
}