#include <stdio.h>
#include <stdlib.h>

int cmp_int (const void *ap, const void *bp) {
  int a = *(int *)ap;
  int b = *(int *)bp;
  
  if (a < b) {
    return -1;
  }
  
  if (a > b) {
    return 1;
  }
  
  return 0;
}

int main () {
  int n = 0;
  int m = 0;
  int a[200000] = {};
  
  int res = 0;
  
  int ans[200000] = {};
  int cnt = 0;
  int is_ng = 0;
  
  int flag[200000] = {};
  
  res = scanf("%d", &n);
  res = scanf("%d", &m);
  for (int i = 0; i < n; i++) {
    res = scanf("%d", a+i);
  }
  
  qsort(a, n, sizeof(int), cmp_int);
  
  for (int i = 1; i < n; i++) {
    if (is_ng+flag[i] <= 0) {
      int k = 2;
      while (is_ng <= 0 && k*a[i] <= m) {
        int idx[2] = { i, n };
        while (idx[1]-idx[0] > 1) {
          int nxt = (idx[0]+idx[1])/2;
          if (a[nxt] > k*a[i]) {
            idx[1] = nxt;
          } else {
            idx[0] = nxt;
          }
        }
        if (a[idx[0]] == k*a[i]) {
          flag[idx[0]] = 1;
          k++;
        } else {
          is_ng = 1;
        }
      }
      ans[cnt] = a[i];
      cnt++;
    }
  }
  
  if (is_ng > 0) {
    printf("-1\n");
    return 0;
  }
  
  printf("%d\n", cnt);
  printf("%d", ans[0]);
  for (int i = 1; i < cnt; i++) {
    printf(" %d", ans[i]);
  }
  printf("\n");
  return 0;
}