#include <bits/stdc++.h>
using namespace std;
const int MOD = 1000000007;
long long POW(long long a, long long b, long long MMM = MOD) {
  long long ret = 1;
  for (; b; b >>= 1, a = (a * a) % MMM)
    if (b & 1) ret = (ret * a) % MMM;
  return ret;
}
long long gcd(long long a, long long b) { return b ? gcd(b, a % b) : a; }
long long lcm(long long a, long long b) {
  if (a == 0 || b == 0) return a + b;
  return a * (b / gcd(a, b));
}
int dx[] = {0, 1, 0, -1, 1, 1, -1, -1}, dy[] = {1, 0, -1, 0, 1, -1, 1, -1};
int ddx[] = {-1, -2, 1, -2, 2, -1, 2, 1}, ddy[] = {-2, -1, -2, 1, -1, 2, 1, 2};
pair<int, int> a[200000];
int c[20], b[200000];
int n;
bool ok(int k) {
  for (int(i) = (0); (i) <= (n - 1); (i) += (1))
    a[i] = make_pair(b[i] >= (1 << k) ? 0 : b[i], i);
  for (int(i) = (k - 1); (i) >= (0); (i) -= (1)) {
    int t = max_element(a, a + n) - a;
    swap(a[0], a[t]);
    if (a[0].first == 0) return 0;
    if (31 - __builtin_clz(a[0].first) != i) return 0;
    c[i] = b[a[0].second];
    for (int(j) = (n - 1); (j) >= (0); (j) -= (1))
      if (a[j].first & (1 << i)) a[j].first ^= a[0].first;
  }
  printf("%d\n", k);
  int now = 0;
  for (int(i) = (1); (i) <= (1 << k); (i) += (1)) {
    printf("%d ", now);
    now ^= (c[__builtin_ctz(i)]);
  }
  return 1;
}
int main() {
  scanf("%d", &n);
  for (int(i) = (0); (i) <= (n - 1); (i) += (1)) {
    scanf("%d", &b[i]);
  }
  for (int(k) = (18); (k) >= (1); (k) -= (1)) {
    if (ok(k)) return 0;
  }
  puts("0\n0");
}
