#include <bits/stdc++.h>
using namespace std;
namespace IO {
const int BUFFER_SIZE = 1 << 15;
char input_buffer[BUFFER_SIZE];
int input_pos = 0, input_len = 0;
char output_buffer[BUFFER_SIZE];
int output_pos = 0;
char number_buffer[100];
uint8_t lookup[100];
void _update_input_buffer() {
  input_len = fread(input_buffer, sizeof(char), BUFFER_SIZE, stdin);
  input_pos = 0;
  if (input_len == 0) input_buffer[0] = EOF;
}
inline char next_char(bool advance = true) {
  if (input_pos >= input_len) _update_input_buffer();
  return input_buffer[advance ? input_pos++ : input_pos];
}
template <typename T>
inline void read_int(T &number) {
  bool negative = false;
  number = 0;
  while (!isdigit(next_char(false)))
    if (next_char() == '-') negative = true;
  do {
    number = 10 * number + (next_char() - '0');
  } while (isdigit(next_char(false)));
  if (negative) number = -number;
}
template <typename T, typename... Args>
inline void read_int(T &number, Args &...args) {
  read_int(number);
  read_int(args...);
}
void _flush_output() {
  fwrite(output_buffer, sizeof(char), output_pos, stdout);
  output_pos = 0;
}
inline void write_char(char c) {
  if (output_pos == BUFFER_SIZE) _flush_output();
  output_buffer[output_pos++] = c;
}
template <typename T>
inline void write_int(T number, char after = '\0') {
  if (number < 0) {
    write_char('-');
    number = -number;
  }
  int length = 0;
  while (number >= 10) {
    uint8_t lookup_value = lookup[number % 100];
    number /= 100;
    number_buffer[length++] = (lookup_value & 15) + '0';
    number_buffer[length++] = (lookup_value >> 4) + '0';
  }
  if (number != 0 || length == 0) write_char(number + '0');
  for (int i = length - 1; i >= 0; i--) write_char(number_buffer[i]);
  if (after) write_char(after);
}
void init() {
  bool exit_success = atexit(_flush_output) == 0;
  assert(exit_success);
  for (int i = 0; i < 100; i++) lookup[i] = (i / 10 << 4) + i % 10;
}
}  // namespace IO
mt19937_64 rng(chrono::steady_clock::now().time_since_epoch().count() *
               ((uint64_t) new char | 1));
const int BITS = 18;
template <typename T>
struct xor_basis {
  T basis[BITS];
  int n = 0;
  T min_value(T start) const {
    for (int i = 0; i < n; i++) start = min(start, start ^ basis[i]);
    return start;
  }
  T max_value(T start = 0) const {
    for (int i = 0; i < n; i++) start = max(start, start ^ basis[i]);
    return start;
  }
  bool add(T x) {
    if (n == BITS) return false;
    x = min_value(x);
    if (x == 0) return false;
    basis[n++] = x;
    for (int k = n - 1; k > 0 && basis[k] > basis[k - 1]; k--)
      swap(basis[k], basis[k - 1]);
    return true;
  }
  void merge(const xor_basis<T> &other) {
    for (int i = 0; i < other.n && n < BITS; i++) add(other.basis[i]);
  }
  void merge(const xor_basis<T> &a, const xor_basis<T> &b) {
    *this = a;
    merge(b);
  }
};
int main() {
  IO::init();
  int N;
  IO::read_int(N);
  vector<int> S(N);
  for (int &s : S) IO::read_int(s);
  shuffle(S.begin(), S.end(), rng);
  vector<int> original;
  for (int bits = BITS; bits >= 0; bits--) {
    xor_basis<int> basis;
    original.clear();
    for (int s : S)
      if (s < 1 << bits && basis.add(s)) original.push_back(s);
    if ((int)original.size() == bits) break;
  }
  int bits = original.size();
  vector<int> permutation = {0};
  int number = 0;
  for (int i = 1; i < 1 << bits; i++) {
    number ^= original[__builtin_ctz(i)];
    permutation.push_back(number);
  }
  IO::write_int(bits, '\n');
  for (int i = 0; i < 1 << bits; i++)
    IO::write_int(permutation[i], i < (1 << bits) - 1 ? ' ' : '\n');
}
