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

#ifndef ONLINE_JUDGE
#include "algo/debug.h"
#define debug(x...) cerr << "[" << #x << "] = ["; _print(x)
#else
#define debug(x...)
#endif

#define int long long
bool isDivisible(int x, const vector<int>& nonDiv) {
	// Use binary search to check if x is divisible by any element in nonDiv
	for (int elem : nonDiv) {
		if (elem > x) break; // Since the array is sorted, no need to check further
		if (x % elem == 0) return true;
	}
	return false;
}

vector<int> printNonDivisibleElements(const vector<int>& arr) {
	int n = arr.size();
	vector<int> nonDiv; // To store non-divisible elements

	// Iterate through the sorted array
	for (int i = 0; i < n; ++i) {
		// Check if the current element is divisible by any in nonDiv
		if (!isDivisible(arr[i], nonDiv)) {
			nonDiv.push_back(arr[i]); // Add to non-divisible list
		}
	}

	// Print the result
	return nonDiv;
}

void solve() {
	int n, m;

	cin >> n >> m;
	vector<int> a(n);
	for (auto &x : a) {
		cin >> x;
	}

	sort(a.begin(), a.end());
	reverse(a.begin(), a.end());
	a.pop_back();
	reverse(a.begin(), a.end());


	auto p = printNonDivisibleElements(a);


	for (auto &x : p) {
		int c = 0;
		for (int j = 0; j < a.size(); j++) {
			c += (a[j] % x == 0);
		}
		if (c != (m / x)) {
			cout << -1 << '\n'; return;
		}
	}
	cout << p.size() << "\n";
	for (auto &x : p) {
		cout << x << " ";
	}
}

signed main() {
#ifndef ONLINE_JUDGE
	freopen("input.txt", "r", stdin);
	freopen("output.txt", "w", stdout);
#else
#endif
	ios::sync_with_stdio(0); cin.tie(0); cout.tie(0);

	int t = 1;
	//cin >> t;

	while (t--) {
		solve();
	}

	// cerr << "Time elapsed: " << ((long double)clock() / CLOCKS_PER_SEC) << " s.\n";
}