#include <algorithm> #include <cassert> #include <cmath> #include <cstring> #include <deque> #include <iomanip> #include <iostream> #include <map> #include <queue> #include <set> #include <tuple> #include <utility> #include <vector> using namespace std; using i8 = int8_t; using i32 = int; using i64 = long long; // using i128 = __int128; using u64 = unsigned long long; using ll = long long; void _main(); int main() { cin.tie(0); ios::sync_with_stdio(false); _main(); } i64 pow(i64 j, i64 n) { i64 res = 1; while (n > 0) { if (n & 1) res *= j; j *= j; n >>= 1; } return res; } i64 n, m; void _main() { cin >> n >> m; set<i64> a; bool zero = false; for (i64 i = 0; i < n; i++) { i64 b; cin >> b; if (b == 0) { zero = true; continue; } a.insert(b); } set<i64> b = a; if (zero) { b.insert(0); } vector<i64> ans; while (!a.empty()) { i64 x = *a.begin(); ans.push_back(x); for (i64 i = 0; x * i <= m; i++) { if (!b.count(x * i)) { cout << "-1\n"; return; } if (a.count(x * i)) { a.erase(x * i); } } } cout << ans.size() << "\n"; for (i64 i = 0; i < ans.size(); i++) { cout << ans[i] << (i + 1 == ans.size() ? "\n" : " "); } }